There is basic math that politicians tend to habitually ignore. As most people who manage their household finance know, budgetary math is actually quite simple. If you spend more than you take in, you incur a debt. If one day there is promise that you’ll earn more than you spend, then that future surplus can go to repay your debt. If that promise does not really exist, you will surely default. If, in default, there is collateral that the lender can grab through foreclosure and the collateral is enough to repay the debt, the lender can come out ok but the borrower not so much.