> What attack is this even preventing - that someone will be able to reverse ssh public keys and get the private? A better approach is to generate a unique key

> What attack is this even preventing - that someone will be able to reverse ssh public keys and get the private? A better approach is to generate a unique key per client so that if you lose access to a device you can remove only its public key. I don't think this is about security. Just about privacy. Some people don't like that they can be identified by their public key. eg (I think) github allows public viewing of a specific users public key, and that allows other services you use with your public key to know your github account etc. It's not a mainstream privacy concern, but there are some privacy oriented people that worry about it.