I dunno, the sidewalk on the six lane stroad near me seems much safer than the fast, congested road with lane-hopping cars and low visibility.

I get it, and I use sidewalks sparingly, but it really is circumstantial (it's legal to ride a footpath where I live). For example, slow riding a footpath is much safer than fast riding a footpath because you have more time to react to cars entering/exiting driveways. If you're riding somewhere nearby that's actually quite a nice experience. But if you are trying to get somewhere more than a kilometre away, slow footpath riding would obviously slow you down a lot.