I agree with you, that .40 and .45 are better at stopping a threat than a .380. In fact, it's seemingly axiomatic that the more powerfuI cartridge is better at stopping a threat. That's why I was surprised by the Ellifritz data, showing that there's not a lot of difference in the real world. I think it has a lot to do with marksmanship under stress (resulting in relatively few CNS hits) and the fact that "stopping a threat" doesn't necessarily mean rendering a person incapable of continuing with his attack but merely persuading the attacker to cease and desist. Hence, a couple of shots into the body from a .380 is persuasive to most. I've also seen videos -- one from just a few weeks ago -- of a cop emptying his magazine into a crazed dude who just kept coming....
And yet, if you make the same argument about the .38S&W/.38 New Police/.38 Super Police/.380/200 Mk.I/.380 Rimmed, etc. loaded to old-school, solid frame, police- and/or military-issue specifications, or perhaps using one of the older Ideal/Lyman recipes, you'll get a dozen flaming posts questioning both your intelligence and heritage.
The 10mm Auto was a Col. Jeff Cooper, USMC, project to develop a longer-range pistol cartridge to replace the existing shorter-range cartridge, caliber .45, ball, M1911, for the United States Marines - and just the Marines. It was meant to be used under combat conditions by an elite corps. When the FBI leadership decided on that cartridge and weapons system as their replacement for a mix of field weapons covering decades of use, they failed to take several factors into account, including Col. Cooper's intended operational mode for the weapons chambering it and the general physical condition and training level of the intended operators.
The .40S&W was designed to replace a combat operative's weapon with a more nearly practical - but similar - cartridge and weapons system for civilian law enforcement. It's a good special operator's weapons system cartridge. Of all the civil law enforcement weapons and service cartridge combinations devised, it is hard to argue anything other than Mr. Roosevelt's favorite, the Colt's New Police .32, was truly inferior to anything in the civilian criminal's arsenal. Yes, certain infamous criminals went beyond the usual shiv or pocket pistol to employ machine guns and hand grenades - and they were pursued by special agents similarly armed. I guess it depends on what you think a neighborhood patrol or highway patrol police officer's duty is: to kill uncivil aggressors or to arrest criminal suspects. I haven't met a uniformed officer yet who though their duty was to shoot people. It's a last resort.
And there's my point exactly: Civil law enforcement and civilian self-defense are two completely different - and at times opposing - activities. As a civilian, I have no duty to execute an arrest. I am under no obligation to protect the civil rights of my attacker. I do not need to secure any suspect for trial. I am not obligated to take prisoners or observe the conditions or the conventions of warfare. My duty is to the life, safety, well-being, and property of those who I hold dear. If the State wishes to prosecute me for defending my own life - and they have before - then I will defend my life in court as well. The State must prove beyond a reasonable doubt that I took a life unjustly - it is not up to me to prove I did not... sadly, these days and for some time now, the State has chosen to use it's power to destroy people who oppose it; proof that any crime has taken place is optional.
The .40S&W is a good and effective cartridge. So is the .22 Short. They simply serve different purposes.