the problem is bicyclists tend to do things that are far more dangerous / serious:
* running red lights
* running stop signs
* driving down the wrong side of the road
* driving on sidewalks
bikes are far less dangerous than cars, which is why nobody minds that they routinely break far worse rules. in addition, bicyclists routinely break the rules you mentioned.
The problem is that these things only seem more dangerous. At the end of the day, momentum kills. Speeding in an automobile, especially in urban areas, is far and away the most dangerous thing of any of the "crimes" here, and it's treated as though it should be expected, not reprehensible as it is.
A cyclist yielding at a stop sign isn't going to kill anyone. The car flooring it after each one and rolling the crosswalks may.
Agreed, and I wish there would be fines and enforcement. Though for half of those you can frequently argue that the biker is avoiding more-common dangers to themselves, like having to squeeze between parked and moving cars where there isn't enough room to do so safely.
In the vast majority of America, including the vast majority of cities, biking is ludicrously poorly supported and heavily favors killing bicyclists over losing a lane. Not that this is any surprise, but it is what it is.
As a resident of Brooklyn, I see cars that do those things more often than bicycles that do those things. (granted, the car driving the wrong way on a one way is usually one going in reverse at 30mph, or a police radio car with or without sirens on)
* running red lights * running stop signs * driving down the wrong side of the road * driving on sidewalks
bikes are far less dangerous than cars, which is why nobody minds that they routinely break far worse rules. in addition, bicyclists routinely break the rules you mentioned.