Do they? Excepting for New York and "last mile" pedestrians, I haven't noticed that tendency much.

Although I also haven't been to any major cities in the southeast, so can't speak to them, and I haven't done any studies, so my impression could very well be mistaken.

Big cities I've been to in Europe, though, tend to have a lot of pedestrians and bicyclists.

You can argue how many cyclists and related vehicles there are in the grand scheme of things but there are a fair number of pedestrians at least during the day in (most?) US cities--that are meaningfully cities and not effectively suburbs that have a mayor.