...and to solve problems with equipment, and to access items that can’t be left unsupervised, and to answer questions, and to observe interactions between customers and intervene if necessary, and to notify management of problems they cannot solve, and, and, and...

You see a pretty clear model today with self-checkout. And it's probably the same even if you make self-checkout better. You have people readily available when things don't "just work."

And the majority of a cashier's job isn't automated away by self checkouts, it's simply passed to the customer...