Do we need central banks? Its not up to us to decide, but the government of each state. We can not influence the solution of this issue. From the point of view of the state, central banks are very necessary, since they perform a lot of useful functions, including maintaining the national money rate, ensuring a uniform financial and credit policy of the banking system, ensuring the implementation of the country's budget and solving many other issues. Therefore, central banks will exist regardless of our desires.
The Central Bank must be needed in every country, to make financial regulations that will become the basis for banks and financial institutions to carry out their activities. For cryptocurrency, I think the central bank is quite limiting, so that its use does not violate the country's law and does not harm the cryptocurrency owner of his country.