They're becoming much more common -- most new apartment buildings since the mid-2010's stack a washer and dryer vertically in a dedicated closet. Less to do wit

They're becoming much more common -- most new apartment buildings since the mid-2010's stack a washer and dryer vertically in a dedicated closet. Less to do with "higher end" and more to do just with designing for it (e.g. washer water hookup, dryer gas and ventilation hookup, and dedicated closet). In many buildings, the cheaper in-unit machines don't wind up being any more expensive to the landlord than the much more expensive heavy-duty machines in a dedicated area over the long run.