In part, it's because organizing politically is only really viable if you disagree on the few most important issues to the public. In order to get political power, you have to either convince a lot of voters that you will fix the economy in addition to (or by) fixing IP law, or you have to convince them that fixing IP law is more important than the economy. Geeks don't necessarily even agree with each other on the top issue of the day, and most systems of government don't let people write IP law without also having a vote on fiscal policy. In order to get elected, you have to convince voters that you will do the right thing with respect to the issues that are most important, not just the issues that are also important. This involves a lot of the sausage-making that tends to be repugnant to geeks, and also a lot of the slogging that prevents anyone from staying up to date on secondary issues as well. They don't organize politically for the same reason that they don't design a new processor architecture to have the Caps Lock key in the right place; the sensible approach is to modify a much smaller portion of the system.
But Cory isn't actually restricting the question to geeks going to Whitehall themselves; he includes the assumption that politicians are corrupt and stupid, which prevents geeks from wanting to try to influence and inform them. There have been times that, for certain processor architectures, you couldn't remap your keyboard (with the software that was available or that you could write). Likewise, some politicians are impossible to influence with good information from geeks. But it's more usual that politicians (or their staffs) would be willing to listen to good information, but geeks don't call them.