Because if they just print the money and add "money printed" to the Treasury's balance sheet, they are no longer pretending that the dollar is bound by some rul

Because if they just print the money and add "money printed" to the Treasury's balance sheet, they are no longer pretending that the dollar is bound by some rules of legitimate currencies, which would surely send shockwaves through the financial system. Yes, there is deadweight loss and time wasted this way, but it prolongs the game of trying to appear to be a fiscally legitimate government, and it ensures that everyone gets something, not just the beneficiaries of existing government works.