I dunno, our species is at the top of the food chain today because we spent the last 60k years perfecting the art of killing.
After animals and plants stopped being a challenge we started killing each other. Then we learned about micro organisms and we've been finding newer and better ways to kill THOSE. Hell, even sharks are in danger of going extinct lately because we're eating all their food.
Friggin' SHARKS, who haven't had to evolve from their current forms much, if at all, due to being so efficient at killing. And we're out-muscling them because KILLING.
Killing is in our genes at this point. It's just what we do, it's a fact of our existence. Hence why Simulated killing is so popular, it provides catharsis for us. I get my bloodlust satiated without actually having to go out and stab someone or something.
That's probably why we don't see many, if ANY, "realistic" games without killing. Realistically, humans are inclined to kill everything.