If people fail to obtain units of the currency, they default on obligations that have much greater value than the value of the all the cash in the currency. Thus in an ordinary currency the incentive isn't to ignore it, or to sell, but to hoard it so that people can't obtain the money to pay their loans in order to create a crisis so that they can obtain a large fraction of the value of collateral.
This is prevented by central banks. If you try to execute this corner, you will drive up prices, so they will start printing money.
So Bitcoin and Ethereum, both remain memes. Fiat currencies have non-mem value due to the debt.