And what would they ascertain from doing that? The vast majority of previous employers either wouldn't be able to speak for very much (outside of massive reliability issues or glaring abnormalities which would surface anyway in most cases) or they simply wouldn't because they'd have no reason to (and plenty of reasons not to).

Hours, training records, DOT tests, eligible for rehire, etc. That's about it and that doesn't tell you very much in most cases.

And while you can't always tell if someone will end up in "the 1%" in an interview, you generally can at least tell if there's something off about them. No system is perfect but don't expect them to start picking people out of a phone book anytime soon.