The number of people is the problem. The more people there are in a general location, the more dangerous people there will be, which will increase the need for prisons, police, etc. If societies were to divide themselves into smaller groups then the need for police, prisons, etc, would be lowered or even eliminated, but most people would have to be convinced to organize their communities this way, which I don't see happening any time soon, so this solution isn't very realistic.