Banks can use blockchain technology but it is never going to be in decentralized manner so it cannot be compared with the crypto adoption if banks starts doing transactions with blockchain.Either bank employees may not let it happen sice if the blockchain was introduced then most of the employment in banks will get vanished.
The development era is more advanced and developing and technology will develop, so will the economic development will also follow it and one of them with crypto currency is an economic system that uses technological developments and banks will also experience system development as well.