Who wants to live in a city if you can work from home? If you are poor and need housing subsidies and there are no jobs for you, there is no reason to live in the city to begin with. People go live where the jobs are. Without "white collar" jobs producing demand for services, there is much less demand for "blue collar" jobs.
If it's just cooping people up, there are cheaper ways to house people than maintaining expensive buildings that need financing and upkeep.