Just because it didn't pass through doesn't necessarily mean it's a bad thing. If it didn't pass through it mist likely bounced around inside a little coursing more internal injury.
Say you hav a BG aiming a firearm at you, it's dark and you can't see behind him, are you sure you still want that round to pass through him? Which could hit an innocent bystander behind him?
But at the same time I do agree with you, why hit someone with ammunition that isn't going to pack a kick strong enough to stop them?