I agree that looks play a large role in many occupations, but I think it goes far beyond that--when employers hire, they subconsciously or consciously ask themselves "does this person look like ---[insert occupation here]?" For example, I know a young, very attractive guy who finished library school with perfect grades, also has a degree in elementary ed, and ton of experience working in the library and teaching children. Yet, he just can't get a job as a school librarian! Why? Well, think. What does the stereotypical school librarian look like? An over-weight, middle-aged woman. He doesn't "look" like a librarian so he can't get the job. Executives tend to be abnormally taller than the average person--why? Because they "look" like executives. The point I am making is that looks aren't just about being attractive--they are about looking like a stereotypical person in your field.
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"To be stupid, selfish, and have a good health are the three requirements for happiness, though if stupidity is lacking, all is lost."
-Gustave Flaubert