I've heard the same, to which I have two replies:

(1) It might be expensive to add a lot of extra plumbing, but is it really more expensive than the revenue your building isn't generating as office space? (I imagine this will vary a lot from one building and owner to the next).

(2) It's possible to have housing with shared bathrooms and kitchens. HN commenters sometimes ask "Yeah, but who wants to live in a place with a shared bathroom?" The answer: someone whose current housing is even worse, or nonexistent. Sleeping in a clean, safe bedroom with a door that locks but having to go down the hall to pee is a big improvement over sleeping on the street.