Why do people say this?

I can't tell you how many times in the restaurant business I've heard "We're never coming back!' I don't understand it. Like do people think after how you treated us we are gonna drop on our knees and beg you to come back. There's this one lady who comes in 10 minutes before all the time to order a very large to go order. She's always so rude about to. We were out of what she wanted and she yelled at me and said she won't be back. "Oh no.... I don't have to deal with an inconsiderate, rude customer." Any time people say that I feel like every worker is just like "You promise!"