Multi-generational homes doesn’t necessarily equate to multiple incomes for support. Historically there was a single income earner because cost of living was more balanced with average income (not true for everyone and every demographic, but on average). Having two or more people in the family earning a paycheck is a modern invention as wages flatlined. I suppose you could go further back when the income was the family farm or business and the kids were free labor, but that’s not really a comparable situation to what’s being discussed.