They reduced the debt under Clinton. It’s a question of political will not physics. US taxes are low compared to their counterparts and they could choose to raise these taxes for various activities.
(It is my personal opinion that the current US Financial situation is due to GWB's presidency. He started this country on this road.)
Social security and Medicare liabilities mostly wiped out any gains
What surplus there was came from both tax increases and reductions in spending. Along with a strong economy and low employment for tax revenue in the dotcom heyday
Any realistic change to pay down the debt would require substantial structural changes at this point. There’s no political incentive to do anything about that until runaway inflation and the US credit ratings start to really mess things up, and by that point it’s pretty much too late
The practical reason for not retiring the debt was that the world needs a zero risk benchmark.
The did retire the long bond, though.