That's kind of the problem with urban planning in many cities in the USA -- the "primary purpose" of roads is assumed to be to serve cars, rather than to serve people.
>You would definitely not just narrow a footpath on a busy high street without considering the impact.
Happens all the time in my city for construction projects - an entire sidewalk will be shut down for years for construction, forcing pedestrians to the other side of the street (which means 2 extra waits for stop lights). Often the closed sidewalk is used for nothing at all except to hold a construction fence.. a more pedestrian friendly solution would require a covered walkway.