This is wild conjecture, but could it be that part of the trend of young people living with their parents is that the older generation has monopolized housing.

This is wild conjecture, but could it be that part of the trend of young people living with their parents is that the older generation has monopolized housing. The baby boomers have clamped down in a historically unprecedented way on the construction of new housing with height limits, environmental and shade analysis, obstructionism in local government, extremely high subsidized housing requirements for new projects etc etc. This has massively pumped up the value of their houses, but now their children can't find somewhere to live by themselves.