If Congress's job is (I don't personally believe this, but I do believe a majority of the electorate does) to influence the population's behavior through the tax and subsidy systems, then why hasn't a very untenable political state been rectified? What I mean is - there is no politician in his right mind who stands up in committee and says, "damnit we need to increase oil consumption - lower the taxes, increase the subsidies. This is IMPORTANT." I think it really speaks volumes for the immutability of policies once they are established.
Hat tip to the Big Picture.