Great, now I'll have the 0.02% chance of surviving a collision with a scooter that slaloms on any possible walkable terrain, instead of a 0.01% chance of surviving a collision with a car that won't hit me because they don't drive on sidewalks.
They do it for the same reason cyclists do it. They value their safety and comfort over the pedestrians'. Riding in the road means cars, riding on the sidewalk means people who will jump out of your way.
