In fact, they never lived alone, there would always be a roommate but that was unusual.
Females lived with their fathers until they were married.
Maybe we are just returning to normal behavior and the aberration has been from 1970 to current?
“...returning to normal behavior...”
Sadly I doubt this. Anecdotal: of my daughter’s early 20’s something friends who returned home, many do sit around and watch netflix and (especially the males) play video games endlessly.
These are the offspring of successful parents, usually, and many went to college.
Luckily our daughters did not move home and made the push to be independent - but the trend within their peer cohort is there and not healthy.