If I had to guess, it's because they seem to value their economic goals/principles over their social goals/principles, and the economic goals are not always the best of ideas.
I think that's a misreading of their principles then. In very large populations with entrenched gov'ts, the individual suffers the most. The smallest minority is the individual, and individual liberties be they economic, social, political, civil.. all revolve around freedom and protection of individual rights. I think theirs are the best of ideas in all areas, and protection of property rights necessarily involves the economic as well as the social.
I won't disagree that they say both are equally important, but I hear libertarians talking about economic issues much more than I hear them talk about social issues.
And on top of that, they seem to caucus with the republicans much more so than the democrats despite the republicans' horrible (from a libertarian perspective, at least) stances on social issues like gay marriage, abortion, and marijuana. Can you think of any libertarians caucusing with democrats? I can think of at least the Pauls caucusing with the republicans.
Aside from gay marriage, I'd say as an individual, economic policies that are very non-libertarian effect me much more than marijuana laws and abortion, which WILL NOT be overturned and is NOT a primary issue for most practical Republican candidates because there are much bigger fish to fry right now. My point is OF COURSE they caucus with the Republicans because economic, property rights are fundamental and effect people much more drastically and completely than do laws against smoking pot, let's be honest. As far as the gay marriage issue, my personal opinion is opposition is waning or at least it's simply not viewed as an important focal point for those that are more concerned with debt, spending, economic growth/freedom, etc.
