It is true that many countries have decided to ban the use of cryptocurrencies, but it is equally true that these bans do not seem to be very effective.  This is because cryptocurrencies are not controlled by a central authority and are essentially decentralized, meaning that transactions can take place outside government control.  However, many governments still try to censor these activities, for example by blocking access to cryptocurrency trading websites or imposing severe penalties on those caught using these currencies.