I don't consider a self-checkout lane to be a "robot" in any sense. It's a customer doing the job of a once trained employee. If you've ever been behind someone new to one of these things, they're slow and annoying experiences.

The main reason for them is reducing workers necessary during slow sales periods (like overnights, or weekday mornings).

And anyway, the job wasn't replaced by a robot in this case. The job was replaced by a customer.