probably one of the dangers of cryptocurrency is when people need it more than fiat. when it happens, it is likely the country's economic system will be disrupted, since most of the state revenues are also derived from taxes on fiat. when people prefer to use cryptocurrency, then fiat will not have a price.
I think impossible people prefer cryptoccurrency there is no guarantee using cryptocurrency. while receipts fiat certainly safe and guaranteed by the government. I think this is not the danger of cryptocurrency