A lot of tools generate UUIDs for the selector, just to get something unique without having to ask the user for something relevant or defining some other heuris

A lot of tools generate UUIDs for the selector, just to get something unique without having to ask the user for something relevant or defining some other heuristic. For instance: the built-in helper tool for Zimbra generates a UUID by default, unless you provide something specific. I think a lot of people assume it should be a UUID just because they see UUIDs used in common examples. Few people think about key cycling for DKIM as it isn't a built-in requirement at all, so once a UUID is set they just keep it until some point in the future that may never happen when they need to revoke the key because the private half is compromised.