> Volatility is a problem for any currency used as a medium of exchange absolutely.

Volatility is not an issue for any major world currency (USD, Euro, Yen, etc). If I pay the bill at a restaurant and ask my friends to repay me on Venmo, the money I receive is worth exactly the same when it hits my bank account a few days later as when the bill was paid. Perhaps you could argue it changed by 0.01% or something due to inflation, but cryptocurrencies can easily change by several percent per day.