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.
I would only add that young people or anyone should be able to afford to live alone as you say OR opt to live with roommates to share expenses and save and build wealth. It shouldn't be necessary for anyone working 40 hours a week to pool their resources with other people in similar situations simply to survive.