(View this answer on Musing.io)
I think you are confusing 2 things. Privacy and security are not the same thing.
Most blockchains are very secure but there is no privacy at all. Since everything is recorded publicly on the blockchain for everyone to view. When you have someone his/her wallet address you can see how much they own and their whole transaction history. Does that sound like high privacy to you? Banksters don't want to use blockchain tech for this reason. "Everyone" has something to hide.
There are however some cryptocurrencies with build in privacy features that make it anonymous. Monero is the best privacy driven cryptocurrency.