I think the benefit is significant. Based on my vivid memories of having roommates, not sharing cooking facilities and having guaranteed quiet and privacy in the evenings are pretty huge. Also having to share space in the bathroom with another person's toiletries, towels, and mess. People forgo lots of income in order to avoid living with roommates because of these issues, so I think it's plausible that they would compromise and accept less income to avoid the worst aspects of having a roommate.

Interesting! I guess it depends on the person. I can see your perspective but for me having someone there part of the time would just be an inconvenience without the benefit of cooking together or socialising together. You're offering the lower risk option (in terms of the potential of getting a bad roommate) so while that probably works for some people most of the ads I see for roommates are looking someone to spend some time with too.

> having guaranteed quiet and privacy in the evenings are pretty huge.

That's a benefit for other roommates, not the landlord. Unless the roommates are the ones subleasing, which is a lot less common.

There is 0 incentive/benefit for the landlord to accept an uncommon arrangement for less money.