I think that cryptocurrency and fiat currency can be used together. The feature of cryptocurrency is that fiat currency does not have, and the feature of fiat currency is that cryptocurrency does not. If there is no fiat currency, how do we buy cryptocurrency, and now various countries are launching digital fiat currency , This is actually a threat to cryptocurrency, because the government cannot control cryptocurrency. It will prohibit the use of cryptocurrency for everyone to use legal digital currency. It will be a blow to cryptocurrency at that time, but we Everyone likes to use cryptocurrency because it is relatively free, not regulated by the government, and there is no third party. Your own information will not be easily leaked, and now transaction payments are more convenient and fast
Digital fiat currency isn't much of a threat to decentralized cryptocurrencies. Digital fiat currencies are a threat to society because they undermine privacy like no tool did ever before. You can't transact anymore without the banks and the government knowing where you were at what point in time and what type of items you most likely bought. If you have to go to a pharmacy twice a week and buy something, they know you must be sick like hell. If you pay the price for a package of cigarettes and they see the exact same amount every day on your financial report, they know you are a heavy smoker.