it is just a service that is offered on money. these services are so many different things. such as loans, credit cards, savings account, Checking accounts, other types of account i don't know the name of in English , Insurance stuff, Mortgages, Safty Deposit boxes, ...
banks doesn't have to be affected by bitcoin or bockchain technology. it is just a different form of money!
I see your point there, banks are for paper money and coins while bitcoin and altcoins are cryptocurrencies. So they should never be a harm to each other, but I think that banks will be greatly affected by bitcoin, in a negative way. Knowing that banks has lots of fees and bitcoins purpose is to send and receive money without any fees, then most of the people, if not all, would rather choose bitcoin than banks. In that way, there will be lesser and lesser people that will use banks, then eventually it will die.