See this girl over there? She said something about you but I couldn't hear

I'm guessing it's because they see looks as useable goods (as in they can use their looks to get stuff). So, it's a matter of envy, like you would envy some one with more money.

Dunno but it's pretty amusing to be hated for such reason.
Like you walk in on your high heels, glossy hair and bomb makeup and suddenly some girl with broom on her head starts whispering.