Treasuries are just an expiring form of cash, when you have money in a checking or savings account that's ultimately a money market "mutual fund" behind the scenes held by the bank to earn a spread

If the gov stopped issuing debt, the cash would disappear as treasuries mature without new treasuries to replace them. In this fiat system, debt IS the money, which is why it's a ponzi... new debt is needed to maintain cash levels in the face of maturing debt (else cascading default and the end of the system as we know it)

The MMT people are superficially right on this, they just dont understand the consequences of perpetuating it.