Amazon/Facebook/Google/Microsoft doesn't let its workers work from home in general. A lot of tech companies don't as well. So moving to CheapSmallTown means when losing the job still having to go back to ExpensiveTechHub to network and find a new job. So might as well stay in ExpensiveTechHub just to be sure.
Imagine if all those large tech companies and others allowed working from home as a default. I think that would be a sizeable economic and cultural shift. It might revitalize various part of the country, small cities and towns. It might reduce congestion, real estate prices in coastal cities.
I work from home and love it. But yeah I am still living next to a tech hub because chances are if I switch jobs I might not necessarily have a choice of working from home.