experimenting

I just heard the phrase "experimenting with drugs" in a movie from 2001. I mention the year because it's not like something from the 60's or 70's. The phrase is probably still in use. The movie is Series 7: The Contenders. It's an interesting sort of commentary on TV violence and reality shows. http://www.imdb.com/title/tt0251031/
Anyway, I'm thinking about that phrase "experimenting with drugs". But do people really experiment with drugs? Don't people just basically try drugs or take drugs (or continue to take drugs)? I'm not used to hearing about kids "experimenting" with cigarettes or alcohol or sex...well, maybe with homosexuality.
So if it's something that's legal or "the norm" for adults but undesirable for kids, then it's something kids get into, involved with, whatever. But if it's drugs or maybe homosexuality, then the kids are "experimenting"? Why the difference? Is it the hope on the part of parents or other adults that once the experiment is done, the behavior will stop, whereas drinking, smoking and straight sex are fine in the long run?