The most appealing part of being a celebrity -- aside from the money, fame, sex, private jet rides, not going to jail for egregious crimes, and the ability to own dozens of mini-horses -- is definitely being able to make a rider.
For the filthy, uninitiated bourgeois, a tour rider is a list of demands and expectations given to a venue before the arrival of a star. Specifications may be made for travel, stage set-up, backstage dressing rooms, and, of course, food and drink preferences. This means celebs can request homemade banana bread, NO CITRUS FRUIT, or even a full, heavily seasoned chicken (all real, actual demands on this list) every time they make an appearance.
Why do we cater to celebrities' fickle predilections? Because they are the equivalent of modern-day sun gods, and we need to appease them. Look, six packs of Lunchables are way cheaper than building a pyramid.