Some aspects of Marxism have a sort of common-sense appeal on first reading. Those of a conservative bent may feel something to be awry, but it takes some sifting to raise, and even then the subtleties foil discussion with those of differing inclinations. Consider Mickey Kaus’s confession of Obamaesque snobbery (via Instapundit):

If Democrats had delivered on the economy, Obama suggests, all those GOP cultural “wedge” issues would lose traction. This idea–that the economy trumps culture–isn’t new. It’s “materialism.” The economic “base,” Marxists would argue, determines the cultural “superstructure.” If the economy changes (i.e. if small town Pennsylvanians get well-paying jobs) then the superstructure will change (Pennsylvanians will feel less intensely about their religion). ..
The problem for me is that I’m a Vulgar Marxist too. I’ve always believed that people need to eat, and want to get ahead and prosper. If you give them an avenue that lets them do that, they aren’t going to let their religion, their music, their sexual habits, their families or their educational system stand in their way for long.

Speaking to the generality first, one should realize that Kaus is shuffling two decks together, here: one insisting that prosperity will ultimately drain the passion from a particular group of values (centrally, religion), and one treating prosperity as a trumping concern. The latter emphasizes that people will not let anything stand in the way of material comfort; the former assumes that religion inherently stands in the way. The former declares what economic success will do; the latter suggests how it may be used.
Thus do Democrats and liberals attempt to make their sheaf of cultural priorities seem necessities riding along with their promise of economic health. They’ll claim that right wingers, with the intention of manipulating us economically, distract the masses with immigration, same-sex marriage, and terrorism, but the left-wingers want to market economic balms so that they can impose amnesties, cultural redefinitions, and multiculturalism.
Moving to the specific expectations of a comfortable population, the modern Marxist’s assumptions aren’t true. Wealth, for example, does not negate religion per se. Indeed, in the long run, a stable home life, defined by sexual control (for one thing) is a more sure avenue toward success than libertinism, but liberals eschew what they see of the judgmentalism of such expectations. It might be more accurate to suggest that they promise their economic fixes to distract from the economic hindrance of their social policies.
If progressives truly believed that their preferred cultural innovations would follow economic success, as a sort of social default, they’d be civil libertarians (and, of course, some are). Modern conservatives, by contrast, tend to believe that their cultural values are compatible with economic prosperity and freedom, but by no means assured. Therefore, they pursue the freedom of other social institutions, such as churches, to have a substantial effect on citizens.