The real reason we're in Afghanistan? Google Taliban and Unocal. One more thing, a former Employee of Unocol (Hamid Karzai) became the new President of Afghanistan after the US invasion.
Regarding the placement of the Unocal Pipeline, a US Official delivered this ultimatum to the Taliban (via the Pakistani delegation acting as their interlocutors): "Either you accept our offer of a carpet of gold, or we bury you under a carpet of bombs." (Ref: Jean-Charles Brisard and Guillaume Dasquie in "Forbidden Truth" (31) (Book's Preface online-pdf format (32) )