Some interesting back-and-forth between Jonah Goldberg at The Corner and Kevin Drum (the artist formerly known as Calpundit) over at Washington Monthly on the question of why liberals seem less interested than conservatives in their intellectual lineage.
Kevin offers the obvious riposte: Conservatism tends to be backward-looking and traditionalist, progressives are, well, progressive. Doubtless something to that, but there remain then some anomalous things to explain. For instance, as Jonah notes, "Postrellians" (I guess that's us) are at least as neophilic as the average liberal. Yet I know that my co-bloggers (and, I'd bet, most of our readers) are as steeped in Hayek, Smith, Locke, Mill, Spooner, etc. as any conservative. Left anarchists (perhaps because there are few enough first-class contemporary anarchist theorists), in my experience, tend to know their Goldman, Proudhon, Bakunin, Kropotkin, and Malatesta. And genuine socialists tend to be similarly familiar with Marx and his forebears and contemporaries. None of these viewpoints are what one would ordinarily regard as "traditionalist."
My own speculation is that contemporary liberalism is much more likely to be associated with an engineering or problem-solving mindset. What I mean is that I think libertarians and (maybe) conservatives are more prone to start with fairly abstract questions (what's the proper scope of government? how are we required to treat each other, in general? what are the preconditions of stable civil society?) and then tweak whatever broad conclusions they come up with to accomodate practical problems. It seems as though liberals more often form their views in a more bottom-up, pragmatic way, as a series of responses to practical problems. That is: People are poor and going without healthcare, how do we fix this? Our schools are in bad shape; how do we fix this? If you start out that way, you're going to care in the first instance about the empirical particulars of contemporary problems, about which historical liberal authors will have less to say, especially if they were more likely to have that same focus. The divide between theoretical and engineering dispositions is probably more likely than any general attitude toward change to explain the difference Goldberg's talking about. Academic liberals in, say, philsophy departments (which is to say, the most theoretically inclined) clearly do have their history down—Richard Rorty cites Dewey and Pierce at every opportunity.