because of the loss of profits. banks are afraid about it. its gonna be real if they dont adopt the technology . but if they adopt the technology of having a blockchain. the end are same still loss of profits. they cannot build a decentralize blockchain for  their bussiness. who people in the world show his confidential documents,transaction in public.  the only thing i think they can build  is a private blockchain in short. (private database) still the same.