Any visitor to a North American city knows that a lot of the geography is designed for single occupant car-based transportation. Anybody who’s spent months in any of these places knows that this car-focused design has been an unmitigated disaster. People are dying, the planet is being killed, and so many other problems stem from building cities for cars.
That badness all being acknowledged, we are at turning point of urban design. The evidence for making our streets for pedestrians over cars is overwhelming; cities which life easier on people are witnessing demonstrable benefits. Those benefits are quantifiable and more research comes out every month highlighting the benefits of desiring for people. Over at Strong Towns they have compiled a great article outlining some of the benefits of pedestrian friendly design.
The cost of paving sidewalks for people is minuscule compared with the cost of paving wide roads for cars, installing traffic signals, paying the salaries of traffic cops, etc. Even the cost of providing enhancements to pedestrian space such as trees and benches pale in comparison to what we spend when we build around cars.
Furthermore, the wear and tear caused by foot traffic is also negligible compared with the wear and tear caused by car and truck traffic, meaning that long-term maintenance costs for walk-friendly areas are also much lower than for auto-oriented places. (Ironically, most cities spend exponentially more on their roads while utterly neglecting their sidewalks.)
In short, a simple sidewalk could serve millions of people traveling on foot for decades, even centuries, with only a small amount of up-front investment and minimal maintenance costs for the city — yet it would support dozens or hundreds of local businesses. The same length of street designed primarily for cars would cost exponentially more to build and keep up and would only serve a handful of businesses.