Let's start with the basics. It never takes a sick day. It doesn't want a raise. It doesn't fail to wash after leaving the restroom.
Once a computer kiosk is used to place the order, how close are we to a fry station robot, a condiments robot and a bagging robot? Raise the minimum wage and reach the cost/benefit crossover point for the major chain fast food restaurants that much sooner.
I can tell you that in the 1990s we were using servo driven, fully computer controlled, bagging equipment for product in a factory. It took the finished products off a conveyor, stacked, compressed, bagged, and boxed the bags for shipping, sending the finished product boxes up a conveyor to a fully automated pallet stacker. The stacked pallets were picked up by a human on a forklift, that driver being the only person involved in doing anything but monitoring the process and feeding raw materials to the upstream end.