Actually, people do; both economic development and democracy spread outward from a very few points on the globe; the closer you are to one of those places, the more likely you are to live in a developed democracy.
But Chris Coyne makes a very convincing argument that
you can't do it at gunpoint. I highly recommend that all my readers listen to Econtalk every week, but this episode is particularly good, and particularly relevant to one of the central policy debates that will decide this election.
This article available online at:
http://www.theatlantic.com/business/archive/2008/04/can-we-export-democracy/3203/