When you say "can I help you?" and then immediately start chatting to your co-worker, do you think you're going to catch my order?
Neither do I!
So why do you do it, over and over again?
And when I get a grande coffee and you charge me for a grande latte and I point it out to you, is it medically necessary to roll your eyes before crediting your mistake to my card?
Because in our society, the correct response is "oh, I'm sorry."