Your public key is something you can share with others, yet control. It's portable to any network paradigm in that sense, thus it also transcends IP and DNS.
However, that is only interesting if you have a confident discovery method. We use PKDNS by placing your signed records into the largest, oldest, most decentralized network on the planet.
You can try and reduce this to "any old name server will do" but every other options falls below PKDNS, even when you reduce it to a basic spectrum.
Should people use more than one discovery network? Sure, we all do, right? We use many identities, agents, hosts, networks, etc. But few of those could be interoperable or support user-oriented graphs.
