Yeah if your only storing username and passwords and hoping no one uses the same username. Now consider I'm running tests on a piece of hardware and storing results in the database. I run 45 tests per unit so I can't use serial number as id, I want a way to get all results for a single unit and I have 5 testers since I'm high volume but each test takes 30 seconds.

Tester 1 and tester 4 might get same pk if offline, random IDs for each record won't work since I can't combine everything for 1 unit. This is more why you use uuids for each test