No that's backwards - the reason is laziness. Sysadmin has two worksations - say a laptop and a desktop. He wants to SSH into all his remote boxen from either.

No that's backwards - the reason is laziness. Sysadmin has two worksations - say a laptop and a desktop. He wants to SSH into all his remote boxen from either. The default reaction might be to just copy his already-authorized private key to his other machine just for ease of use - the proper solution would be to generate a new keypair on the new machine and then copy it to the required remote machines as well, so either can be revoked and tracked separately.