A: There is nowhere to walk to.
In my neighborhood in Albuquerque (Far Northeast Heights), I just went on a walk. As I was walking, I decided to estimate how large each house lot was: 33 of my steps. This means that only about 2-5 people live within 33 steps worth of street frontage. In this situation, a lot of street frontage is required to create enough density for any business to be successful. Though there are nice smooth wide sidewalks throughout my neighborhood, nobody uses them unless they are walking their dog. The closest services are located in a strip mall at the bottom of a large hill.
People will not walk if there is nowhere to walk to.
In contrast, my neighborhood in Tucson has no sidewalks, but many people walk through this area. This is because there are places to walk to. There are two bus routes that intersect a block away. There is a taco shop, offices, a haircut place and two food stores on this same intersection. The lot sizes are smaller, and the roads are arranged in a grid, which allows for easier walkability.
Even though my neighborhood in Tucson does not have the proper facilities for walking, MANY people walk through it because there are places to walk to.
Sidewalks are not important. Destinations are.