Sure but they could move almost literally anywhere else.
If someone said you could live in one of the most desirable places in the entire world on an 'ordinary' job but you had to share a room (which TBH could just be your significant other anyway) that would seem like a great deal right?
A city cannot function without sanitation workers, plumbers, carpenters, electricians, house painters, road maintenance workers, teachers, librarians, gardeners, bus drivers, janitors, delivery drivers, taxi drivers, shop clerks, wholesale merchants, mechanics, cooks, firefighters, paramedics, accountants, bank tellers, municipal bureaucrats, musicians, bartenders, ...
When many categories of essential workers start to be priced out of living locally and need to commute long distances from undesirable far-flung suburbs, it is (a) a grossly inefficient use of resources, and (b) makes the city much less pleasant and effective. A city where all of the residents are wealthy professionals with other workers as second-class commuters is not a very nice place to live, more like a theme park or resort hotel than a real city.
True. Ideally we would have road tolls and congestion pricing to prevent this. With sufficient tolls, something else would have to give whether that's wages or housing.
I'm not saying they are the same or always the case. I'm just saying that is someone is already going to live with a partner, then it isn't a big deal to share a house with another couple.
i.e There is pressure for people living in that area or moving into that area to find a SO or something similar.
If someone said you could live in one of the most desirable places in the entire world on an 'ordinary' job but you had to share a room (which TBH could just be your significant other anyway) that would seem like a great deal right?