To protect life. If an animal charges toward you or your child you are not just going to stand there. You are going to do something to protect human life.
Other than food or for protection against harm/death what other "reasons" do people have for killing animals"
Furs used to be lusted after and so animals gave their lives to accommodate human lust. Some still have the lust
Big Game Hunters whose manhoods are/were in question believed they had to prove their manliness by killing animals, stuffing their heads and mounting them on the man cave Ego walls for bragging rights. Impotent eunuchs all of them.
Ivory is/was desirable so I expect elephants were slaughtered for it though I am not sure of that. Can an elephant's tusks be removed and the elephant live? Of course there would no longer be any means of protecting itself.
Rare animals are coveted to be owned in private enclaves/zoos. The rarer the better. Illegal or not owning is everything. It is another lust that must be sated.
Capture them to put in a zoo to charge money for watching them live out their lives in confinement for the pleasure of those who enjoy ripping living creatures out of their natural environment to entertain while making tons of money. Is EVERYBODY HAPPY?