Crypto currencies have a "trustless" system - i.e., you don't need to falsely trust that the system will work. The distributed ledger blockchain is designed to not need the trust of anyone to operate. Because trust can be taken advantage of via fraud and theft.
Plus, bankers get their power from making currency out of nothing. Cryptos prevent that power from operating. Cryptos also get rid of the middle-man's "cut" in the form of fees. Sure, there are transaction fees for crypto currencies. But nothing like the capital controls of the USA and nearly every other country in the world. With cryptos, you can transfer small or large or mega-amounts of currency without government intervention and oversight. Or banker intervention and oversight and fees. It's outside their control.
Bitcoin and altcoins - their time has come! Because of the fraud and control inherent in the system.