It pisses me off that people think that young Americans are libertarians waiting to be discovered, as if being in favor of pot legalization equates directly with being anti-regulation. Young people are statistically fairly convinced that climate change is a problem worth fixing and they tend to approve of government solutions to poverty and income inequality.
Like paying lip service to a couple no-brainer social issues and non-interventionism will get an entire generation on board.
No, the white male "don't touch my stuff" toddler mentality voting bloc already has a party.
I think if you look at the platforms of actual libertarian candidates instead of seemingly going by your experience with libertarian and Randian idealists, you'll be hard pressed to find a candidate in favor of getting rid of all taxes, privatizing all roads, getting rid of the standing army, scrapping welfare programs (incl. Medicare, Medicaid, Social Security, etc.), completely and 100% deregulating food and drugs (incl. antibiotics), removing all environmental regulations, etc.
To use a couple of otters as an example, there are a lot more Publiuses than there are rothbards out there.
First, I would argue that his following was in love with his personality as much as his politics. But you can be an honest, humble, hard-working little grandpa and probably attract voters no matter what your positions are.
Second, I would submit that "Ron Paul Republicanism" was a thought experiment for a lot of young people - and some older I'm sure - which ultimately just failed, like Ron's bid (well, bids) for the presidency. Which is to say, he didn't lose in the primary and fail to win by write-in because the establishment wouldn't let him play, he lost and failed because at the end of the day his ideas are just less attractive than those of just about any moderate left-leaning candidate, for a solid chunk of young voters.
And so that leaves libertarianism right where it belongs: on the fringe, to be embraced for whatever reason by the occasional intellectual, and to otherwise scoop up the trash (disenfranchised voters) the GOP leaves behind.