I think the role of banks is always important and can never be replaced with anything, even though everyone controls transactions with bitcoin but business and industry will always rely on banks for costs and capital.
yes, banks are more economical and accessible by majority of users, cryptocurrencies will certainly develop into what banks are offering today, but let us be aware that cryptos are not yet widely accepted. and the fact that banks are based per country, the availability of services that banks offers are way to cheap than crypto transactions, people believe in what they see, physically, banks are everywhere, so it is difficult for digital currencies to penetrate the mainstream market.