[magicsmoke]

If you subscribe to MMT, the IOU here is that the government promises not to throw you in jail for failure to pay taxes if you give them some tokens every year. If you own land within the boundaries of a state, and you decide not to answer the door when the tax man shows up, you'll quickly find out how much ownership you really have.

If you decide to go full nomad and never "own" anything, the tokens still work as IOUs in the eyes of the state. Try paying bus fares (public infrastructure fees) or parking tickets (fines/taxes) in bitcoin or gold.

Money is an IOU to be free from state violence in return for economic productivity and corvee labor.