Why do people think that "popular" people are mean?

I think those people are being judgmental either because of past experience with popular people or they are jealous. But there is a lot of truth in the stereotype that popular people are really mean, though and sleep around. Majority of the popular girls back in high school were popular because they were really hot and only hang out with other hot girls, which makes them look stuck-up. I am not too sure about the rumours of the girl sleeping around, any guy could have made that up.