why would they? after all they are public keys, they are supposed to be public. if you really are afraid of github exposing your public key, I think you can always create a separate pair to use only with github.
And in some sense github is doing as a favour, by partially solving the key distribution problem.
If you send me your public key via email, I don't know whether you are who you claim you are. If I get your public key via github, at least I know that you are the person contributing to all those open source projects.
If you send me your public key via email, I don't know whether you are who you claim you are. If I get your public key via github, at least I know that you are the person contributing to all those open source projects.