You're right, and I completely agree that solely using self checkout would dramatically reduce unneccesary, and possibly stressful, customer interactions.

While there are certainly some people who, as employees, enjoy interacting with customers, and even some who enjoy resolving problems and conflicts for customers, I also understand that people who cashier at retail groceries are generally not empowered by management to exercise those kinds of skills.

I also agree with the sentiment that individual human cashiering is "a job that shouldn't exist," although maybe not so completely. There are always going to be transactions which require customer-employee interaction, because they fall outside the more rigidly programmed options available in self checkout. That said, I have watched as self checkouts have grown in both their number and their usage, as the number of employee operated cash registers seems to be declining. McDonald's, for example, doesn't even have cashiers standing at the ready at all times any more. You can go order from a person, at the sole register which exists for that purpose, but you will need to wait for a person to come to you instead of the other way around. Their kiosks and mobile app have made the "row of smiling cashiers awaiting your order" a thing of the past. And I think that level of "self-service" at retail establishments is a well balanced one.