Why should he have? One doesn't tip at fast-food restaurants. At least, not here in Houston.
I do and I'm from Houston:') I often tell them to keep the change or driving off without it at the window. I leave a tip on the table for whoever comes behind me to wipe the table and sweep up the stuff the kids drop on the floor. They work just as hard as the kids at nice restaurants. Maybe harder. I worked at McDonalds one shift and quit when I was in my 20's. I'm a hard worker but ....