Because only trolls are interested in the idea (see the first response in this thread)
As a civil society, we're a little bit past the notion of using violence to solve our problems. Oh, a few antisocial cranks pop up here and there, but the overall flow of events is leading away from violence. And not just in the US... globalization and international trade are making wars between connected states increasingly unlikely. The idea of a major war between world powers is almost unthinkable today. The only places wars occur are in societies that are disconnected from the rest of the globalized commerce & communication among nations.
A good start for understanding this is the book "The Pentagon's New Map" (see http://en.wikipedia.org/wiki/The_Pentagon's_New_Map for a short overview)
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