Many can and do, and that's great, but I don't believe it's happening across the board, and I don't know what makes you believe it is.  My experience is that a majority of people adapt the gun to their lifestyle.  That is why undersize and under-powered guns are so popular.  If what you say is true, the .32s and .380s would die a quiet death. 

I just had this discussion last night with a casual friend who thought a .380 was all he needed.  He's in his early .40s and good shape physically so he certainly has no physical infirmity requiring he carry a lighter gun (not that most .380s are all that great for the infirm, except perhaps for the S&W Shield .380 EZ).  He had never considered the worst case scenario of a drunk or high attacker, one who cannot feel pain, and the need to shut down the physical plant.  He countered with the need to shoot with precision.  I agreed but explained how one's skills deteriorate in a confrontation of that sort, not to mention people's natural tendency not to practice enough in the first place.  Of course he also had the impression the .380 and 9mm were about the same, not realizing the .380 uses much lighter bullets and has often half the muzzle energy, thus is much more likely to fail even with similar shot placement.