It is because of the number of cyclists who pull in front of traffic when they should have stopped, leading to short braking and getting flipped off by the cyclist for some reason. It is as annoying as pedestrians walking out into traffic (not at cross walks or in residential neighborhoods) when there are structured places for them to cross. It is as annoying as a csr pulling through a crosswalk when they shouldn’t.

Even if the overall system is terribly designed, having people create a hazardous situation is annoying.

Anyone who cares that a bicyclist that runs a stop sign or people jaywalk when there is no traffic around is getting their feathers ruffled over nothing. But there are just enough people who walk or ride into traffic when they should be yielding to make it an annoyance.