Normally the government leverages its power to keep its currency stable. If a country fails at that, the residents tend to switch to another country’s currency, for example USD is widely accepted in countries with unstable currencies, and this makes sense, since a lot of commodity prices are set in USD.

What we have seen with crypto currencies are extreme volatility, not useful to base a country’s economy on, and because it is decentralized, no-one can really intervene to control this volatility, by e.g. changing the interest rate, and nothing is priced in crypto currencies, to sort of keep it tied to something.

The only metric for what a coin should cost seems to be the electricity/leasing of computers required to mine one. But even this metric is not good, as it is proportional to the size of the network, which is not a constant, and is likely to grow, as the price goes up.