While I see your point, there is something that you are overlooking. In 99% of self defense cases where a gun is involved, the gun is never even fired. So, even the best, most well trained person in the world is not really any better off than Joe or Jane Guntoter in the large majority of cases.
Of course, everyone who carries a gun should be well trained on how (and when) to use it. But the fact of the matter is that simply having the gun evens the odds against you, even if you don't know how to do anything more than point it at the bad guy.