If a person is working 40 hours a week to contribute to society, then they should be able to afford housing from that society. If a person on minimum wage needs to have a roommate to get by, then that means that their 40 hours a week is not enough to afford their own shelter. Without that roommate, the person goes without a home despite having done their time for society. This is not reasonable.

If it is reasonable for a young person to have flatmates, then that should be because they are a student or an artist and are working only part-time while devoting the rest of their time to their studies or their art.

But a person working full-time? Who may be a single mother or father with a child to support? They should be able to afford a place to live, without roommates.

A minimum wage should not necessarily afford you a median home, that's why it's called a minimum. But for a functional developed nation I argue it should afford you a private room or a very small apartment. Ideally the cost between the two wouldn't be that different, but due to decades of building restrictions the latter does not really exist. This isn't true in Japan for example, where you can find arbitrarily small apartments at correspondingly low prices.

A living wage is for living indefinitely, not just surviving. That should afford more comforts like a reasonable amount of space, a car if needed, and saving for retirement or emergencies.

A living wage shouldn't be based upon what wages a student could be comfortably living on for a couple years before they get their $500k/yr new grad quant job. It should be based upon what people could live on comfortably indefinitely.

It's not "student wage". It's not "struggling young person" wage. It's "living" wage. It's for living - at any age.

Is it reasonable for two people who are dating to have to keep their shared apartment when they break up? What should happen if a roommate becomes flaky or moves out?

These are all real situations that make me think that pinning "living wage" to a level where you have to have roommates is not a good goal. You're basically asking people to survive by accepting unstable living conditions and potentially taking strangers into their homes, which isn't exactly "having your needs met."

Its reasonable, but as we've advanced humanity in so many other fields (medical, technical, agricultural) why shouldn't the base standard of living also be increasing.

Historically it's reasonable for anybody to have roommates. It's a modern scenario where having your own place is supposed to be the standard.

Historically housing was much smaller. And people lived with their families for a lot longer commonly. A lot less was also spent on domestic appliances (not just washer & dryers) and at-home entertainment (a lot less was spent on entertainment in general).

Any adult with a full-time job should be able to afford a studio or small apartment. Probably making concessions on the location depending on where they want to live. It's not a matter of being young or not