It'd be a damn shame when they get shot at for vandalism and performing a hit and run.
They do it because they can. They are simply gone before anyone can do anything about it. I’ve ridden downtown. A car has no chance whatsoever catching, much less keeping up with, a bike that does not want to be caught. The cops are even pretty helpless unless they too are on bikes.
My bike messenger son mentioned that one time he was slowly pushed off the road by a taxi, another event that bent a wheel against a curb. There were a lot of witnesses. The way my son tells it, afterward the taxi was stopped (he had no choice due to traffic) and his window was down. As my son approached, the driver started to argue but my son never said a word. In front of all witnesses he simply pulled his arm back and gave his fist to the driver straight into the face.
He then rode off with a wobbling wheel while the witnesses either gasped or laughed.
I’m sure the other side of the story may vary from this one.