If I'm disabled seem to be more effective for me if I instead use better accessibility device then pushing for sidewalk improvement.
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?