Sufficiently capable devices don't yet exist, and are even more expensive.
Also, you're not thinking about this broadly enough. Sidewalks in bad condition or lacking curb cuts affect way more than just people who use wheelchairs. They affect the blind, the elderly, and even just your every day normal person who trips on uneven sidewalk and injures themselves.
Is it really too much to expect of our government that we have sidewalks that are repaired more often than every century, that are flat, and that have curb cuts at appropriate intervals?
All we want is sidewalks that are maintained as well as roads. They do not need to support as much weight (less materials, less wear and tear). Just needs regular grinding/filling.
“The reasonable man adapts himself to the world: the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.”
