libertarianism as right wing chic
“Radical chic” is an old term from the 70s indicating that a politically liberal person is trying to look cool by promoting radical causes. I think we are now seeing a similar phenomenon among conservatives. Many call themselves libertarian to sound cool, but they don’t actually endorse many libertarian positions except for free trade.
Case in point: The person who defeated Eric Cantor is David Brat, a professor of economics who uses the term libertarian to describe himself. But on a range of issues beside economic deregulation, he appears to be a standard issue social conservative. Immigration? Against it. Abortion? Against it. Foreign policy? Vague. Cutting the military? Nope. Gay rights? Silent. And like many conservatives, cutting government means just cutting the programs that conservatives are upset about, like Obamacare, rather than across the board cuts. If you think that libertarians are socially liberal but economic conservatives, he seems to be very close to a social conservative.
My theory? Social conservatives don’t have a very positive image outside of their movement. Social conservatives have been tarnished by anti-immigration hysteria, anti-Black attitudes, and a strong emphasis on abortion. In contrast, libertarianism is a small movement but has some high status adherents (e.g., many well known economists are libertarians, a number of Silicon Valley billionaires, even a Harvard philosopher). It might also be a political term that is less familiar, so there is less risk in using it.