As long as different states exist, so long will their currency exist. Cryptocurrency will not be able to displace the currency of states, since this requires the decision of the relevant authorities of the state itself. And many different groups of the population will not want to use only cryptocurrency. To use it, you need technical means, the Internet, the necessary knowledge and experience, including for safe use, and much more. In addition, the cryptocurrency has some advantages, and the currency of states others. It is better that citizens always have the right to choose.