Well, first off we have to realize what was well understood a very long time ago. Expanding point bullets are a very old idea. Most people track the concept of bullets deliberately designed to expand to the Express Rifles of the 1870's, but I think it can probably be tracked to the soft lead bullets of the Minie Ball, known to cause horrific damage to people during the U.S. Civil War due to the fact that it was made of soft lead and, upon impact, would deform and expand.
As the New York Times reports:
"The intent of the designers of the rifle musket/Minie ball combination was to increase the firepower of the individual soldier, and in this quest they succeeded. However, in developing a defender's dream, they also created a nightmare, not just for the men felled by the bullet, but for the medical corps stewards and surgeons who had to deal with its effects. The very attributes that increased the bullet's range and accuracy also increased its destructive potential when it struck its target. Unlike a solid ball, which could pass through the human body nearly intact, leaving an exit wound not much larger than the entrance wound, the soft, hollow-based Minie ball flattened and deformed upon impact, while creating a shock wave that emanated outward.
The Minie ball didn't just break bones, it shattered them. It didn't just pierce tissue and internal organs, it shredded them. In addition, if the ragged, tumbling bullet had enough force to cleave completely through the body, which it often did, it tore out an exit wound several times the size of the entrance wound. Civil War surgeons were quickly overwhelmed by the gaping wounds, mangled bodies and mutilated limbs they were asked to repair as the scope of the war broadened and casualties mounted. Though often accused of being too partial to their bone saws, amputating arms, and legs as quickly as the men could be placed on their operating tables and subdued with chloroform or ether, the surgeons really had no choice. Even if they'd had the skills and resources to attempt reconstructive surgery, in the heat of battle they didn't have the time."
Leg bone from the Ragsdale Gunshot Wound Study, 1984, Human distal femur shot with a 510-grain lead Minie ball fired from a .58 caliber Springfield Model 1862 rifle. Photo via National Museum of Health and Medicine, Armed Forces Institute of Pathology, Washington, D.C.
Many militaries took note of this and, in particular, the British Arsenal at Dum Dum in India began producing metallic cartridges with hollow nose and soft nose bullets designed to expand and fragment upon impact. Their experience was that, like the Minie Bullet, these expanding point bullets offered superior ability to wound, kill, and stop over solid, non-expanding bullets. They eventually became so famous that expanding and fragmenting bullet designs became synonymous with the name Dum Dum (but more on that later).
Hunters especially took note of the superior killing potential of "Dum Dum" bullets for medium to big game. Expanding bullets quickly became a favorite of hunters to take deer and up. And this preference remains to this day. Few hunters will use solid ammunition, which does not offer some expansion.
Notice here the confluence of military technology and hunting technology. This is important.
By the 1890's, Great Britain was embroiled in what seemed to be a never-ending series of wars to maintain the British Empire, particularly in India, where they met Thugees and Whirling Dervishes, and in Africa where the Zulu's gave them no end of trouble, (how many movies commemorate this?). The British, to their sorrow, found that solid, non-expanding; bullets simply did not have the "stopping power" of expanding point ammunition and thus, by the end of the 19th Century, were heavily using the technology, to much greater effect.
Also during this time Britain's primary European political opponents were France (has it ever been different?) and Germany, under the Kaiser. The political intrigue, both public and "private" (read spying and backstabbing) was predictable. At that time, Great Britain and Germany were the global "Super Powers." The U.S. was just beginning to step her toes into Super Powers waters, but the European nations had been there long before her and were well established. As part of the political, intrigue both sides played propaganda campaigns against each other. Think of the Cold War, then substitute Great Britain for the U.S., and substitute Germany for the Soviet Union.
As part of this political propaganda, both the Germans and (especially) the French engaged in a broad and enthusiastic campaign to depict the British as being inhumane, barbaric, and committing horrific war atrocities, specifically linked to the use of "Dum Dum" ammunition and ammunition used for "hunting animals." Basically, it was horrific and inhuman to use "'hunting ammunition' on men!" It was positively "uncivilized."
That's a key word right there.
In the Victorian and Edwardian eras, there was an extremely strong sentiment of elitism among Europeans (and many Americans) based partially on the belief that they were "more civilized" than the barbarians of Africa, South America, and the East, thus proving that the barbarians needed to be shepherded and cared for (i.e. "Ruled by our Empire") until they grew up as a culture and became civilized (i.e. "copies of Western culture").
Notice that at this time "machine guns" were in their infancy ("Potato Diggers" anyone, anyone?), aerial warfare was still Science Fiction, and Mechanized Warfare consisted of Battleships inaccurately lobbing shells or locomotive trains delivering troops and cavalry. It was the era of Teddy Roosevelt's famous charge up San Juan Hill.
This helps frame the run-ups to the Hague Convention of 1899.
One of the key arguments of note at the Hague Convention was a measure to ban "Dum Dum" bullets. The British argued against the banning of "dum dum" bullets saying, "Men penetrated through and through several times by our latest pattern of small caliber projectiles, which make small clean holes, were nevertheless able to rush on and come to close quarters. Some means had to be found to stop them. The civilized soldier when shot recognizes that he is wounded and knows that the sooner he is attended to the sooner he will recover. He lies down on his stretcher and is taken off the field to his ambulance, where he is dressed or bandaged. Your fanatical barbarian, similarly wounded, continues to rush on, spear or sword in hand; and before you have the time to represent to him that his conduct is in flagrant violation of the understanding relative to the proper course for the wounded man to follow-he may have cut off your head."
The argument, though quite logical, failed to overcome the propaganda and the British lost that point by a vote of 22-2. Only the Brits themselves and the U.S. voted against the banning of "dum dum" expanding point ammunition.
Notice the one other nation who stood in solidarity with the British on the subject of expanding point ammunition? Yes, the United States.
Notice anything about the dates? Hague Convention of 1899. The Moro Insurrection of 1899.
Hmm... During the Philippine Insurrection of 1899, the U.S. serviceman complained that the current issue .38 caliber, solid non-expanding, bullets were failing to stop Moro warriors and "traded up" to the .45, right? Well, the reason that the U.S. voted with the British against the banning of "dum dum" expanding point ammunition is that we knew then what we know now. Expanding point ammunition "stops" more reliably. We voted with the British because we wanted to use "dum dum" ammunition in the Philippines! When that was no longer an option, and we were forced to use solid, non-expanding bullets, we made the quite logical decision to just up the size of the bullet itself.
Knocking Out the Moros, via U.S. Army Art Collection
However, the U.S. Service Man there in the Philippines was generally unaware of the political gymnastics of global Super Powers half a world away from him. All he knew from his perspective was a simple 4-Bullet Point liturgy.
-Moro Tribesmen high on drugs with bound up limbs trying to hack me apart with swords and stuff so I shoot Moro Tribesman with Service Issue .38 LC revolver chambered with Standard Issue solid nose bullets.
-Moro Tribesman fails to fall down after .38 caliber chunks of heavy stuff enter Tribesman's body.
-I complain and Army gives me old .45LC revolver with which I shoot the Moro Tribesmen high on drugs with bound up limbs trying to hack me apart with swords and stuff.
-Moro Tribesman falls down - Success attributed to superiority of .45 caliber chunks of heavy stuff entering Tribesman's body.
The "obvious" conclusion, as far as the Service Man was concerned, in the absence of knowledge of the run up to the ammunition change over, was ".45 greater than .38." If it occurred to him that the .38 could been stepped up in lethality by making it Expanding Point, his observation was drowned out by the legion of his fellows exclaiming "bigger = better!"
They didn't need to consider the relative merits of recoil, ammunition weight (or capacity), or issues of expense in discarding .38 chambered revolvers for a different chambered handgun. All he knew, or cared about, was "Moro barbarian no longer trying to hack me apart." And then he repeated the story at home and it got magnified ad infinitum until now it is considered God's Own Truth, handed to Moses himself on the 3rd Stone Tablet.
So, all of you .45ACP fans... You're in love with the round not because it's "better" than expanding point .38-caliber ammunition but because the French were scared of magic exploding bullets of doom used by the British! mu-hahahahaha!