That works IF there is a deterrent to back up a neighborhood watch. If there is nobody to report to and no actual response then a neighborhood watch is nothing more than organized witnesses crying to the sky. It will still give a semblance of success if no actual threat materializes.

The problem is how to respond to crime, particularly violent crime, when no other deterrent exists. As all of history shows, the only response left is to meet force with force. That then (hopefully) creates a new deterrent. More often than not that new deterrent becomes the new problem.