I have not personally experienced this but given the videos I've seen, the comments I've heard, and the accident reports I've seen, this might boil down to "I haven't harmed anyone YET."

Acting in an unacceptable manner until you manage to hurt someone isn't really acceptable in a bike scofflaw any more than it is in a drunk driver.

There needs to be a standard of behavior, or some people will abuse the system. It's difficult to design a standard of behavior that works without rigid guidelines.