Consider that parents may have children in their mid 40s. These children are effectively dependent until ~20. Often they'll accrue significant debt to pay for college. Then 10-15 years later their parents may need significant care. If those parents weren't wealthy or careful to save then these children could find that they've few if any years free of heavy financial or caretaking burdens. Then consider they may want children of their own.

The lack of a real social safety net in the US really feels like previous generations pulling up the ladder.