Why do girls throw themselves away like that!?

Hi, hello. Sometimes it really bothers me how girls just don't hesitate or anything and throw themselves away. Even in my grade I know of so many who have and it makes no sense. They are in high school and probably wont ever see the guy after graduation. Oh and then moving in together...he won't even marry you then. At least not for like 10 years. Also statistics show that if you have sex before marriage your guy is more likely to stray off and cheat on you than if you wait until marriage. Sorry gents I am just stating the facts.