If you have worked in the service industry before, you know that even some of the seemingly most pleasant people are terrible tippers. However, if you make a point to provide fast, seamless customer service to every person who walks through the door you have a better chance of getting tipped generously.
If the interviewer asks you this question, assure them that you give excellent service regardless of the tip percentage. When someone tips poorly, you just brush it off knowing your hard work will be rewarded, even though it may not be in the form of a generous tip every time.
"One of my most memorable customers was an elderly gentleman who would sit at my bar every day from 3PM -5PM before going home to make dinner. He drank two vodkas on the rocks and had some great stories to tell. He always tipped just .25 cents, and I thought it was adorable. You don't know everyone's financial situation, and it was more important to me that he had somewhere comfortable to come when he was feeling lonely."
"Not everyone is a great tipper, and others are excellent tippers. It all works out in the end, and I don't take it personally."
"That's a great question! When I was new to the service industry, this bothered me because I took it personally. I would think 'Did I do something wrong?'. The truth is, I knew I was doing a great job! Now, it doesn't' bother me in the slightest. I am great at what I do, and if a customer doesn't always appreciate my craft, that's okay with me."