Yes, I agree the point should be not to miss. But I dont think it is practical to think you will hit your target everytime, so stray shots are a big issue.
Fairly often you hear stories along the lines of "Police fire 15 shots, bad guy struck twice).
Statistically speaking, in that kind of situation, a bystander is many times more likely to be struck by a stray bullet than an overpenetrated one.
I also agree death is not the primary goal of an armed confrontation, but it is surely my secondary goal. Obviously, the first matter of business is to stop the attacker. If the attacker dies, though, everyone is really better off.