Bank can transfer faster but not the same with how faster using bitcoin and altcoin, if bank adopting with blockchain technology we can transfer money to other country just few second, if using bank transfer we need more than one day for receiving money to other country, but not possible if bank want to adopt blockchain technology because bitcoin and altcoin not have stable coin price.
First you need to understand that anyone can implement blockchain technology for their services like transaction which is irrelavant to the prices of coins.Banks started using blockchain technology for transaction but not for every transaction,maybe for their internal transactions they were using,it is not going to affect the crypto currency in any way which also using same blockchain technology.