Banks already have infrastructure and customers. Slow walk to the digital coin and then suddenly, that is the only option. You have to put yourself in the mindset of the typical person. If you look at it through your own lens, it wont make sense how it would work. We went from gold to paper to checks to credit cards to debit cards to googlepay/applepay/etc. So what is the obvious next step? A bank isssued digital currency. Its the natural and logical progression.