Why do chimps kill chimps from other groups that come into their territory? Why do some chimps use aggression against other chimps to manipulate them, while other chimps use grooming?
A certain degree of sharing is part of our human / animal nature, but so is a certain degree of claiming ownership over things, and certain individuals have more sway over decisions than others. Flat hierarchies with nobody in command seem to work in theory, but in practice it’s different.
That’s the Naturalistic fallacy at work, though. We aren’t chimps, nor is doing what humans did in the past necessarily better than what we do now. By that chain, you would be an Anarcho-primitivist.
You’re a mammal, a rat is a mammal - should we just consider you the same as a rat?
But we aren’t chimps, and you shouldn’t judge the effectiveness of economic structures on what chimps do.