It's too early to talk about derivatives at this stage, when average joe could not even get their wallet working securely  When the wallet is stolen or lost or broken, then the derivatives related to underlying assets will be shaken badly

The reason that bank exists is mainly for security: General public have a one stop security solution for all their money in a bank. But from time to time you could hear that someone lost his 2fa secured wallet on blockchain.info   And you have a whole bunch of technical and strategy challenges when it comes to offline cold storage