Not my experience at all in the downtowns of NYC, Boston, Seattle, and SF. DTLA is a very unique downtown due to many factors specific to LA (mainly car culture taking away practical significance from the city center + the housing sprawl) and that doesn't generalize to most actual cities.

> Security is absolutely necessary in down towns. In LA, it is out of control. You can't even go inside a 711 without being harassed until they hired guards.

At which point the need was filled. No dystopic community mercenary forces were necessary.