there are several factors why banks are reluctant to adopt bitcoin:
1. No feedback: that is to say they don't feel a positive feedbacks generated from bitcoin nurturing, in fact, their products will be much abandoned.
2. Risk: extreme fluctuation rates make banks reluctant to use it, as it also deals with the risk of bank shareholders
3. Government: the bank is one of the data sources for the government so that if it is related to anonymity, it will be difficult for the bank to prepare the data in case of examination.