Most Helpful Girl
It's kind of like a vicious cycle isn't it? Beautiful girls are used to getting approached all the time, and so become used to it and assume that any guys that like them will surely approach them. Inevitably, the only guys that have the guts to approach them are the "beefcake a**holes" that esper88 described (thank you), and so the pool of guys the beautiful girls have to choose from are limited. Eventually the beautiful girls wind up with the beefcake a**holes (having no other options/are not socialized to make the first move themselves), all other guys see all the beautiful girls with said a**holes, and it perpetuates the stereotype that the beautiful girls only want that "type" of guy. So, all regular guys figure that they never had a chance and never try, and it goes on and on.
All it boils down to is insecurity: if beautiful girls weren't so insecure to approach the regular-type guys (because those guys seem to not like them), and if regular guys weren't so insecure to approach the beautiful girls. You can't blame one party or the other.