> This naively (or maliciously perhaps) maintains that the "purpose" of the certificate is to identify an entity. [...] identity is not the primary purpose certificates serve in the real world.

Identity is the only purpose that certificates serve. SSL/TLS wouldn't have needed certificates at all if the goal was purely encryption: key exchange algorithms work just fine without either side needing keys (e.g. the key related to the certificate) ahead of time.

But encryption without authentication is a Very Bad Idea, so SSL was wisely implemented from the start to require authentication of the server, hence why it was designed around using X.509 certificates. The certificates are only there to provide server authentication.