I personally think it is expecting a lot of anyone to be as proficient as possible with a handgun for a couple of reasons. For one thing, it's expensive, going on very expensive, besides in a lot of cases, going on impossible. There just isn't enough range space to go around, at least if everyone did that. Even so, when I go to the range, there's a line all the way round the room of people waiting to shoot.
Another thing is that you simply cannot keep yourself at the peak of perfection forever. By that, I mean nothing more than the simple fact that you lose your physical abilities over time. Young people won't believe that. On top of that is diminishing returns of additional practice. You're only going to be so good and in fact, I believe additional shooting will even reduce your abilities. I won't go out on a limb and say how much is about right, though, but that's been discussed in other threads.
Judging from what I read, most civilian encounters are nothing like what the police do, and likewise, most successful civilian use of a firearm were not by people who were highly trained or experienced in what just happened. Chances are, neither will the police. From what I understand, policemen who are involved in shootings will find themselves in assignments of less risk. As for civilians, the law of averages is on their side. Of course, trees fall on people's houses all the time where I live but the law of averages is still on our side.