The primary purpose of a bank is to issue debt. That’s why they were created. A bank has to be able to “print” money to issue debt. This isn’t a flaw as some crypto fans like to think, it’s a very important feature. Debt issued by banks replaced the informal promise-based debt people used before we had banks. You didn’t need money on hand, or to borrow some coins from some rich dude, to get help building a barn. You got help from people in the village in exchange for some other goods or service you’d provide them in the future. Bank issued debt with “printed” money is the replacement to that, and it only works if money can be created on demand.
Crypto can’t “print” money on demand, by design. So it can’t replace banks.
Another thing banks do is, Alice is in New York and wants to pay Bob who is in Miami, or Kyiv, so instead of getting on a plane with a sack full of Benjamins she tells the bank to send money to Bob. Cryptocurrency is clearly an alternative way of doing this, with the advantage that then there is no middleman to refuse the transaction when the bank is being leaned on by a despot.