Killing is the easiest way to get lots of calories and building materials. Plants do it, too.
We're hardwired to have empathy for our own kind, e.g. the "selfish gene" theory, stronger for kin than for strangers but nonetheless strong enough to create an almost universal taboo against eating people. Note however that many other animals do seem to be wired to eat some of their own children: https://en.wikipedia.org/wiki/Filial_cannibalism
"The most dangerous game." People are very resourceful, and furthermore have friends and family who hold grudges. Eating people is a bad strategy because people who make a habit of it tend to get killed for it sooner or later. Hunting nearly anything else is safer than hunting other humans.
https://www.amazon.com/Red-Queen-Evolution-Human-Nature/dp/0...