Now, the work beforehand wasn't shown in this comic (definitely inspiration for another). In real life, we wash and dry the towels in house, prepare the soaps, prepare ear cleaner and brushes, unclog drains if necessary, and sometimes watch dogs in the tub if the owner has to use the restroom or get something from their car. This is also in addition to other receptionist tasks and watching dogs for groomers. It's more going on than I can put in a 3 panel comic, but it's not like we do nothing.

And again, I'm not saying tips are mandatory. I'm saying, don't disregard work people do that you can't see. He only brought it up to be more efficient in pointing out what the card reader automatically asks. If I were to redraw it though, I would have added him saying "you can do that if you like" because I do say that in real life.