They're not just more fickle, the underlying ideology that drives both movements is dissimilar. American conservatism is resentment as politics, which is why pissing and moaning gets the 20 whatever percent of the country that decides everything for everyone to turn out again and again. Continued Republican failure to immanentize the eschaton doesn't drive them away, it just makes them more and more resentful, and more and more lockstep. In contrast, even the most insufferable wonk aspires to (more often than not nebulous) societal betterment. Sure, that aspiration might lead to loathsome nonsense like (no strawperson) means testing the gas tax, but dude, at least it's an ethos.