Why do Wheel Chair user's take to the Street?

The reason I do at times is that the sidewalks are uneven with some sidewalks resembling stairs. For myself I have bad disk degeneration in my spine and neck and dropping off a 1 inch uneven sidewalk is akin to being Pile Driven into a wrestling mat. Broken and or bad spines are what have landed quiet a few people in chairs. These sidewalks in this condition can even cause a person to be thrown out of their chairs.
Who is responsible, and what can be done.
Well in most cities the landowner is responsible for the upkeep and care of the sidewalks including snow removal. In the city of St. Louis there is a 50/50 program where the city will pay for half of the cost of replacement. Also the landowner can be hit with a law suit for personal injury on his property. While this should be a final option, it will get people off their couches and out fixing the walkway.