Even if not for anything related to customers they may end up doing it as a test, sure that won't be official and be used but they know they need to check out blockchain and how it works so they will make a new blockchain currency for themselves and they will definitely want to implement the best parts of blockchains into a currency, that would have been something awesome but we still don't know if they are doing it or not. Sure they must be working hard on figuring it out but not sure if they have implemented any parts of it.
Some banks are working with Ripple for some huge movements we know that but that's about it. Banks need to adapt because if some banks implement it they will make it cheaper and faster so they will get ahead of the competition and all others HAVE TO work on it to catch up so it is going to get common eventually.
I would see this as duplication system because it would involve people have the coin for different bank, and that coin, what exactly would it be used for? To be able to buy things In other sites? So how many coins does an ecommerce site want to accept before they are known to accept cryptocurrency, this I don’t think banks would want to create their own currency.