Because it isn’t a good money for the modern age. It doesn’t transmit value well across space (uniform, verifiable, acceptance). And - for the last 50 years - it hasn’t been better than real estate for transmitting value over time (credit access, limited supply)

Both have flaws. But the United States defecit and debt have been enabled by the credit system supporting US real estate as a form of “money” storing value over time while the dollar resulting from credit expansion transmits value over space.

The two together in the digital age were pretty powerful for many decades…though that game has been played out.