Why do we need a blockchain or a merkle tree? We have TLS, SSH, PGP, a number of VPN solutions...blockchains and merkle trees are consensus and versioning protocols, not security protocols. Their use of cryptography is orthogonal to the traditional security goals of confidentiality and authentication.

The problem is that incentives aren't aligned. Companies don't care about your personal data they only care about your metadata, so they won't invest resources into protecting your personal security. TLS, SSH, PGP are all communications protocols, they provide no rules concerning value exchange, which is what account creation is. When you create an account on a 'free' platform, your de-facto making an exchange of data for value. The issue here is that the transaction is one-sided because there are no guarantees on personal security. If your account information follows you around the web in the form of a public key, then your in control of your personal security.