Typically, administrators want URIs are identifiers that administrators want to hide as much as possible from end users, but it doesn't mean we want them to be totally opaque identifiers like GUIDs. It is often useful to actually look at the URIs when troubleshooting, and when that happens it's very hard to tell at first glance if an assignment is correct if all you have to look at is a GUID or something equally cryptic. URIs don't have to be self-documenting or even especially user-friendly, but they should be meaningful to humans. This way they can be memorized, transcribed and understood more reliably.