Multi-generational homes are as old as the human race. Everybody being expected to leave when you're 18 is an incredibly new concept in the grand scheme of things.
North American individualism. The path we were promised was get education, get job, get apartment, meet so, merry so, buy house then have kids. The American dream is very 1D. Let alone paying taxes, "If they take one dollar off my wages, I'll vote that bastard out!!" . We're a very individually selfish people..
Yea I called it "North Americans" we Canadians are quite guilty as well:C. Ontario killed subsidized housing.. I got a 5k down payment for my first home and they cut subsidized housing by 40% bitter pill...
Coincides with how small living arrangements got so that more houses could be sold. Any relatively new concept should be cross checked with how capitalism has been fucking up what should have been a liveable society.