I wouldn't say banks are too afraid, I'd say they are being prudentially cautious. Banks have very different standards when it comes to reliability. This isn't about some system losing clicks, or likes, or whatever. Here, every single mistake can cause significant financial loss.

Just think what would happen when client trades get stuck at some point during execution. If market prices develop unfavorably in the minutes or hours until the error is fixed, the bank has to take the loss, on every single trade.

Almost all people I know who work in banking (including myself) would love to get rid of our legacy systems, but that's much easier said than done. Especially since many of those legacy systems are inter-connected.

VaultOS is based on "smart contract" technology that allows people to tailor their own products such as mortgages, loans, and overdrafts.

Those are nice new features and all, but none of that means anything if you can't replace the existing core features first.