I think it's because being a cooperative is not a stable state. You can go cooperative->traditional, but it's much harder to transition from traditional->cooper

I think it's because being a cooperative is not a stable state. You can go cooperative->traditional, but it's much harder to transition from traditional->cooperative. Ultimately, a hierarchical society is instinctively easy to grasp, while a more fluid mostly-equal one is not. People still instinctively understand hierarchies better than full-on democracy.