When these things start happening (Pinkerton) it's because there is a need that isn't being met by the state. This tells me the state is not providing the type of policing the populace wants.
Sure, but they did more than that supplementing law enforcement where it was deficient like providing "secret service" to Lincoln, pursuing "Western" outlaws, like the ones robing banks and trains, etc. Before the FBI came into existence it had some of that role because the state was not providing it. Arguably, with the strikers and such, the state was absent from the dispute when it should have been there mediating.
Point is, if the state is not providing these services, then the demand will make it profitable for someone to fill the role.
