Good question Zrex,
It may just come down to the fact that many hunters plain just don't care much about the animals you mentioned.
Seems like some care if they wound a deer but the other animals it just doesn't matter that much.

I'm not saying this is for all hunters but I would say there are some with this attitude and that is why you don't have the outcry when you speak of headshots on these animals that you do with deer.