Why do we, as a ‘free’ people, need so darn many law enforcement agencies?
Because of people like bandidos and cossacks who have no restraint in having a shootout in a public place.
Heck if they wanted to meet, to discuss motorcycle safety, down in the river bottom where innocent people are unlikely to get hurt or killed and shoot it out, I’ll donate ammo.
I never thought of this until I read your question. Having many agencies may turn out to be a good thing if massive civil unrest breaks out. I doubt if all would be willing to follow the same orders. (emphasize "may")