Public keys are not meant to be public. They can be public in that making them public doesn't compromise the corresponding private keys. And generally making them public helps scale key management.

There are cryptographic protocols where public keys are kept private. For example TLS with client certificates (the client's certificate gets sent encrypted to the server). Ditto SSHv2 (the client need not reveal all its public keys, and it does get to authenticate the server before revealing its identity and public keys).