If you teach people how to be happy and play nice, you do need as many hall monitors. Teaching is the crime prevention aspect of police work. The other part is more like garbage collection. Somebody has to clean up the mess and figure out who made the mess, so you do not have to clean up the mess again.
Nobody in their right mind goes out of their way to become a garbage collector, but if you do wind up one, you better come to grips with that it is just a job and you are not going to change the human animal in the process. People do seem to go out of their way to become police or politicians. We might want to put better psychological screening into people who want to become law enforcers or law makers. You see fewer prideful people seeking retirement after twenty years as a garbage collector.