Where in the United States do you see space within existing urban areas that people live/work today, where there is empty space for high density housing, transit, retail, etc, which does not abut or live on top of low density SFH suburbs?

Because I've lived in a few of the largest urban areas and the answer is "nowhere near the jobs."

So you're saying that they build giant malls, office building, and (what is left of) manufacturing in cities by tearing down SFH?

Certainly, not what I've seen. So people coming for "the jobs" DESERVE the kind of nearby, low cost, transit friendly housing that does not currently exist, while the people who live there DESERVE to have it taken from them at a price lower than the housing will currently bring?

Why?