In the words of Satoshi Nakamoto, the pseudonym of its founding father: “The problem [with a central authority solution], is that the fate of the entire money system depends on the company running the mint”. In this case, the mint is run by the institution that issues currency, in other words, the central bank.
I do not refer to the existing products as currency because they do not perform any of the key functions of money. While activity may be too small right now to be systemic, at some point they could have financial stability implications. The crypto world is moving fast, and is largely unchecked.