This is probably my #1 head scratcher as I walk/run/bike/drive around here, always has been, lived here 34 years. With covid, I understand why some walkers and runners will move off the sidewalk and into the bike lanes or roadway as they pass by other pedestrians. I'm good with that, people who do that seem to jump back on the sidewalk as soon as they get by. It's the walkers and runners who eschew the sidewalk that I never understood.
I used to run 1500+/- miles/year, these days it's more like two-three 3-5 mile runs a week and for the last 20 years I've coached a college XC team. I've had runners tell me (and read on this thread) that an asphalt road is softer than a concrete sidewalk. While I believe that's technically correct, no matter what the surface is - asphalt, concrete, gravel, mondo, dirt, grass - the softest part of the equation is the shoes the runner or walker is wearing. And IMO the part of the activity that leads to the most shock absorption is how one runs/walks (stiff vs fluid). Choosing to run on asphalt vs concrete, or for that matter grass or a rubberized track as opposed to harder surfaces... In 40+ years of being in running I've not yet found any study that definitively shows that runners can expect to have a lower incidence of injury when they run on softer surfaces regularly. "The data are mixed" is a phrase that comes up time after time.
But, people are going to believe what people are going to believe and other than the runners I coach I don't think what I think is going to move them. So I'll just continue to be entertained when runners are in the street if they think it's because running on asphalt is going to be a lot softer than running on concrete.