When bikes approach intersections at speed, it's pretty easy to spot the vehicles at or approaching it. They have bulk and presence. But to clear pedestrians you've also got to check 3 or 4 corners. Sometimes those corners are even occluded by parked cars as you approach.
So what happens time and time again is bikes don't notice pedestrians entering the crosswalk until it's too late to stop at the speed they're going. So they end up veering around the often very surprised people who did not expect a bike to blow right past them from out of nowhere. This is a rather disconcerting experience, and it leads to a HUGE number of complaints.
Note, I am a big supporter of proper bike infrastructure, think it's worth removing parking spots for it, think it's worth installing traffic lights for bikes, separated elevated bike lines, and all that.
But I'll say this: San Francisco is not Idaho. We have so much more density. The busiest bike/pedestrian intersection in Idaho can't hold a candle to the wiggle. Rolling through stop signs at even moderate speeds is not super compatible with heavy pedestrian traffic.