Earlier quoted context omitted.
As the father of 18 year old who is not going to college and instead working as a carpenter, I don't think lumping 18 year olds with 25+ year olds makes much sense. Perhaps I have an antiquated view of family, but I don't feel his "independence" has everything to do with where he lives. I'm more than happy to have him around the house if it allows him to save money and live a better life at, say, 21.
This is spot on. Multigenerational housing used to be the norm, not a symbol of failure. Why we all think it's a great idea to leave our families at 18 and pay high rents so that we can live with strangers we found on the internet is beyond me.
It's more difficult to maintain a romantic relationship when living with family (especially if both partners live with family), and it can also delay life skills (e.g. learning how to cook at home, clean, and generally learn to live more independently; though it's possible to deliberately learn this while living with family, it becomes a necessity to learn after moving out).