Elfmama wrote long ago:
"But I think the picture of the chicken, hamburger, or whatever, is necessary because of illiteracy rather than innumeracy."
The pictures of food joke goes way back, but it has nothing to do with illiteracy. Illustrated consoles were mostly designed to simplify accounting and speed up the ordering process. Up front, the cashier just needs to select what the customer ordered by item, and internally the computer handles setting up the order, tracking the inventory and throwing the price up on the screen. If changes need to be made to the price of a product, the cashiers don't need to worry about it, they just select "chicken sandwich". If the store runs out of onion rings, one update tells the console to disallow ordering of that item so the cashier immediately knows what to tell the customer. Pictures of the product speed up "reading" the console for most people, even highly literate people, so they can find what the customer wants quickly and get the kitchen staff working on making it that much faster. All of this was designed to streamline ordering, cut down on pricing problems and simplify the training process, not because the people working the counter are generally not smart enough to handle the old way.