For the same reason people kill most animals: tradition and they're delicious.
I've heard of vegan, vegetarian, pescatarian, etc., but it would be interesting if there was another eating style based on some (admittedly challenging) evaluation of the animal's cognition or social behavior.
There are some vegans and vegetarians who subscribe to a "no pain" version of this which allows eating creatures like oysters who verifiably can't feel pain.
I've heard of vegan, vegetarian, pescatarian, etc., but it would be interesting if there was another eating style based on some (admittedly challenging) evaluation of the animal's cognition or social behavior.