You know, I've never felt the urge to bike down the sidewalk, and I don't think I ever see anyone else do so.
But that's probably because my area has decent cycling infrastructure, so that means I have a place to cycle without fearing for my life besides the sidewalk.
Then you've never lived in Salt Lake City, Utah, where drivers seems to consider bikers (even in bike lanes) as targets to harass and scare off the road (and even to throw 7-11 full "Big Gulp"s at), and crosswalks as "pedestrian target zones"…
I live in a city where it’s legal and it’s never bothered me. People don’t ride fast on the sidewalk. It’s mostly old people who just wouldn’t be riding at all if it wasn’t legal.
But that's probably because my area has decent cycling infrastructure, so that means I have a place to cycle without fearing for my life besides the sidewalk.