No trainer, private, LEO, or military, teaches to "shoot to maim." You shoot to -stop- at center mass, where you have the likeliest chance of actually hitting your attacker and doing immediately incapacitating damage. If the person ends up dying that is an unfortunate side effect.  

Aside from the extremities being harder to hit, and a miss doesn't stop an attacker, they are also more likely to allow a shot to pass through and endanger others further downrange.  The irony of shooting extremities is that hits will not reliably stop an attacker but can potentially kill them later. There are no safe places to shoot at someone to "wound," too many large blood vessels can be damaged that can end up killing. It's also potentially a way to end up in jail. Lethal force, using a gun, is only justified by a lethal force threat. By shooting to wound you are implicitly stating the threat wasn't life-threatening, making your use of lethal force in response viewable as criminally disproportionate.