Bitcoin is not centralized electronic currency, it is a decentralized digital currency. Where did you see such wrong information that bitcoin is a centralized currency?
Bitcoin is possible in physical form like Casascius Bitcoin which contains the private key of an amount of bitcoin but government will not make such project to move forward.
Thanks for correcting the OP, Bitcoin is a decentralized digital currency, that is not owned by any country, and it doesn't have any central office, if it becomes a physical currency, then the purpose of it's creation, would be defeated. If Bitcoin becomes a physical currency or cash, then it must submit to a central bank that will regulate it's printing, meaning that it'll them become centralized and that privacy that comes with holding it will not be possible again. I think that Bitcoin is better off being a digital cash than a physical one, the only thing that we need is massive adoption, so we can carry out transactions anywhere in the world.