First, understand that there's a difference between authentication, authorization, and encryption. You can have a fully unencrypted method of authentication or authorization, or you can encrypt either or both.
However, cryptographic signing methods allow you to authenticate a document, a person or a bearer, from which point you can decide whether that entity is authorized; further, if you use a form of public key encryption to do so, you can then encrypt data so that only that individual can read it.
For example, https offers both authentication ("This host is trusted by someone I trust, e.g. Verisign"), and encryption ("The data passed between me and this host are unreadable by the outside world,"), but authorization ("This person or entity has access to this data") is another process entirely.
There are some (rather esoteric) problems that could, theoretically, be solved by a more efficient version of something akin to blockchain, but in general it's just a poor tool for most applications. But people treat it like a STM treats his favorite torque wrench: ratchet, prybar, lug wrench, crowbar, window rest, wheel chock, drift, bearing press, buss tie, hammer ... largely due to failure to understand what it is, and more to the point, what else is out there.
