You miss the point. The tank can continue to fight or opperate with as few as 1 crew member left. It won't do so very efficiently, but the fact of that matter is that it WILL continue to opperate.
GVs are completly different from planes most regards, and should be treated differently from planes. That means no "your driver is wounded, so we sent you back to the tower

" BS.
Driver wounded: you can't move, same as an engine hit
Commander wounded: you revert to the old driver view, or to the turret view
Gunner or loader: unable to fire, same as damaged turret
You should have hit all of these crew members before its considered a "pilot kill" as in a plane.