My suburban neighborhood growing up did not have sidewalks; not sure if that was unusual. Overall it's my impression that urban areas are much more walkable/bikeable than suburban ones. At the very least, it's difficult to leave or enter individual subdivisions in the suburbs on foot (by design).

Try going to the grocery store in the suburbs on a bike. Sidewalks are great for walking your dog. But in the suburbs, you are trapped to your car.

You can't walk, take the bus, or ride a bike anywhere. Not only because it's 10 miles away, but because there simply is no safe way to get there without a car.

Sidewalks have been a feature of every city center neighborhood I've lived in (and I've lived in many). Cities can be safer in that I rarely drive and there are visible and predictable pedestrian street crossing everywhere. While pedestrians do get run over, it's at a far less frequent rate than car-on-car accidents happen.