It would be stupid to have a cash lockbox like Gore and Bush recommended.
You have to invest the funds somewhere, and US treasury notes are still considered the safest investment.
If this was a completely standalone agency, you wouldn’t be able to say that. If they invested in corporate bonds, there no funds there either. Corporations only issue bonds so that they can spend the money. Same with US treasuries.
Gold, land, oil reserves - there are plenty of assets with substance out there rather than a treasury bond from a debtor that comes up a trillion dollars short in paying its financial obligations every year.