I guess because animals (eg tigers) eat other animals (e.g deer) and have evolved exactly towards that purpose. That’s how their species survives.

It’s not often that I see a tiger performing sexual assault on a deer. That’s not required for the tiger’s survival.

Now whether humans are “naturally” meat eaters and therefore we should feel “better” about eating animals I don’t know. Nutritionally I think the evidence probably leans towards being omnivore, similar to many other apes and monkeys.