This is wrong, it's like saying that cars and planes are the same because they both have wheels.

Banks, as well as a lot of other industries are using cryptography for secure communications and user authentication. In Bitcoin it is used for user authentication and establishing consensus in decentralized environment. These systems are too different to simply reduce them to "cryptography".
Also, people are right to doubt cryptocurrencies and blockchain, they are still new and experimental, and only few coins like BTC or LTC can be considered safe. There are many examples of crypto projects having bugs and vulnerabilities that result in severe loses for their users, so being "blockchain" doesn't mean that it's secure and trustworthy.