There is also the resistance to change angle. If a party (in this case the banking system) is presented to change it needs to decide whether to adopt, adapt or ignore as a reaction to that change. For companies, who have to deal with investors, the primary decision tool is whether a choice is economically viable or not. Otherwise said, banks feel they have little incentives to adopt Bitcoin. That might change in the future, but even if they do, big companies can't adapt to change as fast as startups. You have an already established company culture, then you have to deal with company learning, technologies, etc. Another way to look at it is that it would affect some departments a lot.
It's notoriously difficult to get banks on board with new advertising concepts, and so they go on making mistakes like these (
http://thefinancialbrand.com/37549/6-mistakes-in-banking-advertisements). If banks don't want to learn and improve on mainstream concepts, how are they to handle Bitcoin?
This doesn't mean they won't, it just means it might take a while.
