I agree with @delegate that human interaction is valuable; sometimes I choose a cashier lane instead of self-checkout because I prefer it. But even then, half of the interaction has been delegated to the screen on the pin pad.

And, I'm all for people having careers that are meaningful and fulfilling. But, is supermarket cashier the most valuable thing these people can be doing?

Imagine we had all the money we wanted and could pay people to do anything and buy robots to do anything. What would we choose to buy robots to do and what would we choose to pay humans to do?