The whole decentralization is to move away from big banks who happens to run by big government. Now lets not be naive as bitcoin and other block chains become more utilized by everyday people there will be know way in hell that uncle sam will not try to either be part of it , run it , or try to do away with it since as for now they have now way of stopping this juggernaut call crypto currencies . To answer the question we don't need them it will scaled on its own just like the internet grew by the want and need of the people.