I think parents and others push against these things and it peaks the superior undying curiosity in every child - the moment they can; they'll try it to see 'why not' . . . It's not that they *try it* when they're children / teens; it's that when they're children/teens they're merely victims of their insatiable curiosity and fall prey to their own rebellious nature.
For those who don't have these issues = they wont' suffer the consequences.
For my kids I think the death of their cousin and their grandmother at the fault of drug-abuse was iodine on the wound of the 'need to know'