"Snitches get stitches". So it's usually the smart thing to do is just to stay out of it if it does not involve you.
That's a BS street line, and a BS excuse. If you're living on the same street as the criminals that are destroying your neighborhood, and you pretend it's not happening, you are no better than the criminals victimizing your neighbors. You should be required to report everything you know to the police. When you remain silent, you are condoning the behavior, allowing more people to be victimized. Same thing with those Hollywood bimbos who kept silent when sexually assaulted by a move producer, just so they could keep their movie role. They never thought about the next woman that would be assaulted in the same manner. Then they have the nerve to come out 20 years after the fact to whine about it.
In Medieval times, if people in a village knew a crime had occurred, and knew who the criminal was, yet remained silent, the whole village was fined by the King. If somebody in the village discovered a body, and failed to report it to the authorities, they were held accountable. There were plenty of snitches back then that would turn you in. People that live in crime-ridden neighborhoods should be fined for not cooperating with the police. Maybe they'd finally decide to police their own neighborhoods. Even convicts in prison police their own cell blocks and dorms. When a troublesome inmate brings unwanted surveillance from the uniformed staff down on their block or dorm, the other inmates will confront the troublemaker, and take care of business. I know that for a fact, because I worked in uniform in NY State's prisons for 25 years, and saw it happen many times.