The same reason that the FBI (and other policing administrations) did away with the service revolver. There's actual a distinct tragedy where some FBI agents died in a firefight that spurred this, apologies for lack of citation - it is late.

It is scarily easy to miss, even at physically close distances, when fighting for one's life.

I feel most people that haven't shot a gun, or have only shot a gun while sitting perfectly still and undistracted, underestimate the above fact.

If you do have access to guns and the ability to test this, do some sort of exercise to get yourself breathing heavily before shooting, you'll see the difference.

All of this presupposes that we agree the average citizen has the right to defend their life with adequate tools. Some may, with good statistical arguments at hand, determine that the likelihood of being a victim of violent crime does not meet the threshold for allowing this level of self defense.

I hope that partially answers your question