Why are teens so stupid?

I'm 16 years old, and I'm a girl. just to put it out there, I'm not some adult complaining. The thing that really gets me down is that people my age engage in drugs and . And I know it's not my business, but it's just the level of stupidity that comes with it. Like, I understand weed, but when they decide to do heroin and strong drugs just really annoys me. Well, weed too, because it becomes a habit to them and that's all they want to do. The gets me down more. Girls giving it to older guys just because "OMG hes so cute <3", guys being taking advantage of girls with no repercussions. I don't know, I'm not saying I'm a saint, but I've never done stupid **** like that. Am I just too mush of a square haha because it's so hard to relate to others. It just saddens me because I never realized this was sort of "normal" and people are totally okay with it. Shallow relationships, lusty , reckless drugs and parties. I mean, I know it's not all of us teens, but it seems like A LOT of us are just plain retarded. Just why? What drives people to these behaviors? :/