The disagreement on the “devalue” thing is probably one of semantics: I value the employee as a fellow human, but I don’t think the job of cashier is providing any value to me.

The existence of “cashier” as a job is an impediment to my goal: paying and walking out of a store with the goods I want. Any alternative system which involves fewer cashiers works quicker for me, observationally.

I think people - including cashiers - are inherently valuable. But having someone do a 1-1 cashier job is both wasting their time and costing the company (and me) unnecessary time and money. Their (valuable) labor would be better spent elsewhere.