Metal gear solid 2 had an awesome reactivity to hit locations. Shot in main arm => can't shoot for shit anymore. Shot in leg => only limping. Shot in both legs => prone.
It's a great way to increase immersion, add impact to weapon hits and keep the lethality of combat. I wish more games used similar systems.
Actually aiming for body parts gameplay over realism I suppose. I guess in reality nothing trumps the increased chance to hit of aiming for center mass.
If the impact of a hit in specific body parts is only stat loss (like in Ja2) than it makes little sense to actually aim for very specific body parts. Because we go on to kill that enemy anyway, whether or not he lses 5 points in aglity or not. Conversely, our characters permanently or temporarily losing 1 or 2 points in agility or whatnot is just a silly annoyance adding very little to the game.
I even think aiming for the legs in Ja2 was rarely a good option. If you hit, and the enemy fell down (which wasn't granted) then the follow up shot s against these downed enemies were harder to hit than follow up shots against a standing enemy, where you could aim for the head. So often time, chest or head were the only real options.
Assuming hits in very specific body parts have more interesting effects (like disabling the enemy from moving or shooting or forcing him to drop heavy gear or whatever) then that could be a nice option. Maybe a bit of a filter could be applied that such aiming would only be allowed if the enemy was reasonably close to the shooter and not moving or only moving slowly. That way, it would be disabled as a choice in situations where it's really ipossble to the point of being nonsensical. Bullets may still hit specific parts of the body by chance, though