Agreed.  I PERSONALLY will not want to put my Bitcoins in a bank but I can also recognize that not all 7+ billion people on the planet think the same way.  I think sometimes people respond from a point of view that "X wouldn't be useful for me therefore X isn't useful for anyone on the planet".  

Cryptocurrencies won't end the banks.   If (and this remains to be seen) they are widely adopted they could change the banks but there will always be banks as long as there is money.  There have been banks longer than there has been fiat currencies.  Sometimes I get the feeling that people think fiat currency has always existed.  It is a relatively new invention with significant adoption only in the last three centuries.   Modern commodity money (i.e. standardized precious metal coins minted and certified by a national authority) has been used for almost three thousand years.  The first "banks" were essentially gold vaults with a ledger of account balances kept by the bank.   Merchants received gold, merchant was afraid gold would be stolen, at the end of the day merchant deposited his gold with the "bank".  Eventually banks starting issuing receipts and merchants began trading the receipts directly because it was cheaper and easier than removing the gold every day.

If Bitcoin becomes large enough it is only a matter of time before a bank offers the ability to exchange Bitcoins for fiat currency and offers depository services.  As for banks being prohibited from dealing in anything other than fiat well that is just nonsense.  Most banks already offers the ability to buy and sell shares of stocks and mutual funds.  Some banks in China sell Gold (yeah the actual physical metal).  The customer pays by bringing in cash or by drawing against their account and the bank delivers the purchased gold on the spot.  I don't know if any of them offer depositor services or rebuy the account holders gold but that wouldn't be much of a leap.

Another angle that is at least plausible, involves one or more exchanges becoming a bank to reduce compliance costs.  It may sound crazy but nationally chartered banks are exempt from state money transmitter laws.  It is much easier being regulated by a single entity than being regulated by fifty or more entities.  It may not be a bank which has a branch in every major city, it may not even have a single customer accessible branch but it would still be a bank.  Credit card issuers are a good example of this.  Technically one doesn't need to be a bank to issue credit cards however as money transmitter laws sprung up in various states, most issuers found it easier to reorganize as a nationally chartered banks and have one regulator than be classified as money transmitters by multiple regulators.  Today all major credit card issuers in the US are banks although many of them have no "branches", hold customer deposits, or offer any other banking services.  CapitalOne, American Express, and Discover are all nationally chartered banks in the US.