Girls and guys your age (girls especially) are in such a rush to grow up. They see sex and sexual humor and sexy clothing in every movie, magazine, and television show. It's really hard to ignore, and it also becomes difficult for 13 and 14 year old girls to figure out where they fit in with all this sexuality in the media and society in general.
They're not necessarily being "stupid", they are just unaware of the things that should be important to them at their age; friends, family, school, fun stuff. Sadly, that stuff isn't "cool" when you're 13 and 14 anymore; sex and parties and other pastimes are more widespread among young teens than ever before.
I'm proud of you for not following the crowd. Good for you!