Or pay them to do something useful, but not profitable in the market. For example, childcare. Or taking care of old people. These are totally useful jobs, but babies and retirees don't have money.
The adults supporting them no longer have triple the income to afford to pay for the lives of their children and their parents.
Exactly, and that's what taxes are supposed to be for: finance useful activities which aren't handled adequately by the free market. But before moving some workforce to those jobs, we first need to acknowledge this workforce as available, i.e. unemployed rather than employed at something pointless.
Part of what fueled the industrial revolution was the number of farming hands which went unemployed due to agricultural mechanization: they became industrial workers.
The adults supporting them no longer have triple the income to afford to pay for the lives of their children and their parents.