I attended a very good innovation meeting last week and there one senior banker said that innovations in banks are so difficult because there is an obsession with business cases. No innovation investment is allowed to fail (is this attitude imported from credit risk evaluation?) and the endless business case argumentation actually puts innovative people off. If this would have been the case in society at large not much innovation would have taken place.
But of course there are other reasons - like the fact that much of innovation has to be done together with competitors to succeed- creating rulebooks and standards for payments, e-invoicing, cards, trading, e-id etc. This is both difficult and against competitive people's basic spirit and you can get to move forward with the speed of the slowest (if all have to agree - as is often the case in bankers associations). This again leads to the nimble banks trying to break loose and do it on their own - successful only in small countries.
and many more here: