Police resources can only do so much and can only be in so many places at one time so it is important for citizens to take some responsibility for their personal and neighbourhood safety. Meta-analysis shows that neighbourhood watch reduces crime by about 16% (Source, see "Summary of the results"). It also aides in an investigation because it informs neighbours with cameras that a crime has occurred and they can check their video for a possible perpetrator or suspicious vehicle, something that likely would not happen without a watch.
It is free and therefore one of the cheapest ways to protect your property and neighbourhood. Automation has made it almost effortless so there is no reason not to sign up and start a neighbourhood watch.
