Hierarchy tends to prevent violence by providing an authority to appeal to. So long as there is some process people can take, in hope of redress, they will choose that instead of just stabbing a motherfucker. This applies to interpersonal conflict with your neighbor, or mass conflict between religious groups, indeed everybody seeing a fat old baby commit high crimes on national television. Even if you feel the odds are abysmal, that can be enough to stop you from grabbing your pitchfork with intent to use it.

Belief in those systems is a finite resource.