Public key authentication is more secure than nothing, and is more convenient than shared secrets and symmetric encryption, but bit for bit the secret material necessary for public key cryptographic schemes to be secure is more data than is required for symmetric algorithms.

But more to your point, public key cryptography is basically a usability nightmare. In order to talk to anyone you need to first validate their key using an entirely out of band scheme you already trust, and if you don't do that then all the end to end encryption in the world is theatre.

Of course I'm being hyperbolic, it's the internet, but seriously there a lot of people feeling secure with public key systems that are either totally insecure, or could be insecure and they wouldn't know, or are secure to some random bystander but insecure to people and organizations that are often included in people's threat models.