Because tax revenues have plummeted. Tax cuts under the George W. Bush and Trump administrations are responsible for 57% of the increase in the ratio of the debt to the economy, 90% if you exclude the emergency expenditures of the pandemic. The United States is nowhere close to the average tax burden of the 38 other nations in the Organization of Economic Cooperation and Development (OECD), all of which are market-oriented democracies. And those cuts have gone primarily to the wealthy and corporations.