Cars can avoid bikers more easily than pedestrians. You don't walk around with rear-view mirrors.

A bike rear-ending a pedestrian is going to be much worse than broken bones for both. A bike rear-ending a car is just going to hurt the biker.

The solution you're looking for is for people to not ride bikes if they don't want to take the risk.

I'm pretty sure sidewalk building codes are also written to assume they're not a bike path. You're more likely to run into blind corners on the sidewalk (and thus risk a collision) than a bike lane.

You've also forgotten about disabled people using the sidewalks.