For a simple practical example, it's awfully useful for a lot of systems to be able to generate UUIDs in an app while offline (think document creation, etc) and

For a simple practical example, it's awfully useful for a lot of systems to be able to generate UUIDs in an app while offline (think document creation, etc) and reconcile things later by shooting the blob of content off to the server, while knowing that you only need to handle the dance of getting IDs and updating stuff locally again in your error handling case.