The cops are stretched very thin... Damn little patrolling, pretty much just reacting. And they know that if they do anything, they are just gonna see the perps kicked out of jail, sometimes on the same day. The city prosecutor doesn't bother to send her people to frickin' murder trials - so the defendants walk.
About a month ago, a raving crackhead pulled out of a gas station, clipped my parked car, and totaled her car and an acquaintance's car. The police responded, as did an ambulance. They let her go. They didn't search the car. They just got her daughter's number, and she was picked up. No insurance, of course. "If we take her in, she'll be out by tomorrow, but there will be reams of paperwork." And you gotta be sensitive to the poor accident victim's needs and requests...