Not everyone wants to live with their parents and extended family. I like my space, and my privacy. I would not want to live with my parents, or other adults other than my wife. Kids need two parent households, and other adults don’t replace your mother and father. It also helps shape your view of relationships. If you never saw a man taking care of your mother, you’re probably the type if a woman asks you to lift something heavy, you say, “What would you do if I wasn’t here? Or, “What you gonna do for me?” A woman raised that way will always challenge what you say, for the heck of it. Can people grow and evolve? Sure, but never date expecting someone to change.
And nuclear families are working just fine for everyone else as far as both parents being in the home.