This is a genuine question.
Banks embracing blockchain technology is like record companies embracing peer-to-peer technology like Bittorrent.
If you take a look at a traditional currency like the euro, you see two prominent institutions: a central bank and a bank.
The central bank regulates the rules of the currency.
The banks administrate who owns what.
If you compare this to a cryptocurrency like Bitcoin, these institutions have been replaced by software:
the Bitcoin protocol defines the rules of the currency.
the Blockchain administrates who owns what.
The banks seem to be embracing the component of the architecture that was designed to replace them.
How does that add up?