Libertarianism, especially among the young, is indeed predominant. Eighty percent have premarital sex, and a high percentage shack up. They support redefining marriage because it meshes well with their general penchant for promiscuity, and want to do drugs, drink Bud at football games, and abort away our future rather than study or settle down and get married at a young age.
What you describe is not libertarianism - which is simply a political philosophy of minimal government - but at best a list of things libertarian governance would permit. And note that premarital sex, shacking up, drinking Bud at football games, not studying, not settling down, and not getting married at a young age are all already legally permitted; are you suggesting that if not for the alleged dominance of libertarianism these things would be illegal?
The “minimalist” government you talk about springs directly from atheism.
Ayn Rand — and most other libertarians (as Murray Rothbard writes) are atheists. Atheism is exhilarating, particularly for our hormone-addled youth who care little about boring economic libertarianism. Abandoning the Ten Commandments/go to church God liberates our youngsters to vote for what they really, really want to do — live in a world with no restrictions on sex and drugs. Atheism is heart and soul of libertarianism.