Because it went horribly in Vietnam? Because we have tens of millions of willing, ready, and able volunteers? If you ask me, compulsory duty is just a bad idea, period. Especially in a country the size of the United States. It all sounds fine and dandy if you are not at war, but what if your two years just so happened to be 2004-2006? What if I turned 18 during that period? I get to endure decades of PTSD and who knows what else just so I can master the fine art of driving a Humvee?