How and why do culinary artists plate their dishes?

Culinary artists typically plate their dishes with some kind of unique presentation. This can be done by drizzling a sauce on the meal or adding garnishes and such. Their plates are always very clean and pristine in a way that would somehow make the dish more appealing. Sometimes they use a color contrast between the dish itself, and the meal that sits upon it. Typically, a meal that is more pleasing to the eye, has a much greater chance of being eaten/enjoyed by the consumer. Have you ever watched a commercial and said "oh, that looks good, I'd like to try that sometime,"? Well, there you go.