1. You don't have to be licensed to bike on a road, but you do for motorized vehicles. This doesn't make sense.
2. Bikes can't keep up with traffic. I have to sit behind bikes trying to get up the SF hills daily, and either have to perform semi-dangerous passes or wait while cars back up behind me.
3. Bikes break road laws way more frequently than cars. Blowing through red lights and stop signs like they don't exist, which is dangerous for the biker, the cars, and especially pedestrians trying to cross the road.
E-bikes with a biking test/license would solve most of my issues.