I think it's possibly a bit naive to say banks are "unsure".  The banks are fully aware of the reasons why they aren't pursuing this technology.  The main reason being, they don't actually stand to benefit much at all.  There are effectively two options for banks:

• Option 1 is the fake "blockchain technology" the mainstream media keep talking about, which is still a private walled-garden where the company maintaining the "blockchain" (read: database) is in total control.  The customers won't actually see any difference in practice, so it would basically amount to a monetary investment in developing a great big pile of 'nothing new' if they went down this route.  It's still traditional banking but with a slightly different way of storing the data.  Who cares?

• Option 2 is a true, decentralised blockchain, where users have control over their funds.  But if you have a profitable business model where your customers are effectively reliant on your services, why would you risk drawing attention to a technology that puts regular people in control of their money?  Real blockchains remove the need for middlemen.  That's a threat to their profitability.  So it's a no-brainer as to why they won't pursue that.

You can certainly try to fudge a mix of the two (and I'm sure loads of companies are looking at that exact thing as I type this now), but unless they've got an absolute goddamn genius in their midst, I don't see them pulling it off without making some serious compromises that would significantly limit the appeal to customers.