Minimum wage is often paid by some of the most physically and emotionally intensive work—service industry jobs. Having to work in a hot kitchen all day or deal with irate customers while being paid less than you need to survive is not exactly the best situation to be in.
Anyone who has worked in a customer facing position has had to deal with a customer demanding a manager at least once. Sometimes, they have a valid concern, and it's just something that's out of your hands. Often, though, they're misinformed or just upset and making everyone's lives more difficult.