In his post arguing that the failures of the Iraq War are likely to be repeated, Jim Fallows makes the following point:

After Pearl Harbor, after Vietnam, after World War II, after the 9/11 attacks, even after civilian disasters like the Challenger explosion or Katrina, there were official efforts, of varying seriousness and success, to find out what had gone wrong, and why, and to yield "lessons learned." That hasn't happened this time, for a lot of reasons. 

For the Bush Administration, there was no "failure" to be examined and explained. For the Obama Administration, the point was to "look forward not back." People in the media and politics who were against the war know that it can grow tiresome to keep pointing that out. 

Example: Barack Obama would not be president today if he had not given a speech in Chicago in October 2002, saying that he (as a mere state senator) did not oppose all wars but was against a "dumb" and "rash" war in Iraq. Listen to how he talked in those days! He also denounced "the cynical attempt by Richard Perle and Paul Wolfowitz and other armchair, weekend warriors in this administration to shove their own ideological agendas down our throats, irrespective of the costs in lives lost and in hardships borne." Because of that speech, six years later Obama could argue that his judgment had been right, and the vastly more experienced HIllary Clinton's had been wrong, about matters of war and peace. But there's no percentage for him in bringing that up now.