PGP keys are associated with emails and there are various fully decentralized options to discover these keys (keyservers, WKD, ...). (How) does Keypub improve on this?
Use SSH keys for SSH connections and authentication
Use PGP keys for email encryption and file signing
Keep these systems separate as they're designed for different purposes
SSH is a common tool which most developers have installed, keep in a working order, use often, and reasonably understand.
Guess which tool is easier to piggyback on and achieve easier and faster adoption.