Gives those who get a kick out of war and conflict something to do that isn't lob nukes at each other. Same reason you want layers of government with progressi

Gives those who get a kick out of war and conflict something to do that isn't lob nukes at each other. Same reason you want layers of government with progression at a small scale available to many. So all the people with political ambitions aren't all trying to start their own governments and revolutions. Busy is stability.