It’s about resources in general, not just the federal budget.
Suppose I borrow money from the feds and make an investment in physical capital which afterward makes a high rate of return. We can say society benefits from the increased efficiency – that’s arguably why the return is so high. But clearly I’m benefitting, too, from the part of the return which accrues directly to me.
“Ah, clearly this was a good investment”, the feds say, as they wipe away part of my debt. What has happened? The dissolution of the debt has increased my ability to claim and consume yet more societal resources, even in excess of the return on the machine.
Production is finite. Those extra resources I claim will be because I outbid others with what was gifted to me.
One could rightly argue, in most other circumstances, that production is finite but not fixed: my wise investment increased total production, and the extra resources I claim for myself comes precisely from that extra productivity of the physical capital in which I invested. I claim more, because my investment created more. That is the standard argument, in fact.
But that does not include the original debt.
It is the ability to repay the original debt which signals the worthiness of the investment. When I am gifted with not only the return on the investment, but also forgiveness of the loan itself, the extra resources I’m allowed to claim benefits me in excess of my marginal contribution to total production.
This is true on top of any tax issues. (Which are really federal debt and inflationary issues, which are yet more complicated. Tax revenues are only part of the equation there.)
If the individual return exceeds the societal return, the cost is greater still.