Why not? Right now, compromised account keys give you the ability to issue certificates that are valid about as long as certificates are valid (or, in the worst

Why not? Right now, compromised account keys give you the ability to issue certificates that are valid about as long as certificates are valid (or, in the worst case, +90 days from the original expiration date). Just about any scenario where the account key is compromised is one where the certificate's private key is compromised as well (not to mention typically one where you can just solve another challenge), so you're not really in a much worse position. Even less of a concern once authorizations are valid for only ~7 days.