Or because he would have said something like this:
WASHINGTON -- The chairman of the Joint Chiefs of Staff is expected to advise President Bush to reduce the U.S. force in Iraq next year by almost half, potentially creating a rift with top White House officials and other military commanders over the course of the war.
Administration and military officials say Marine Gen. Peter Pace is likely to convey concerns by the Joint Chiefs that keeping well in excess of 100,000 troops in Iraq through 2008 will severely strain the military. This assessment could collide with one being prepared by the U.S. commander in Iraq, Army Gen. David H. Petraeus, calling for the U.S. to maintain higher troop levels for 2008 and beyond...
According to administration and military officials, the Joint Chiefs believe it is of crucial strategic importance to reduce the size of the U.S. force in Iraq in order to bolster the military's ability to respond to other threats, a view that is shared by Defense Secretary Robert M. Gates.
Pace is expected to offer his advice privately instead of issuing a formal report. Still, the position of Pace and the Joint Chiefs could add weight to that of Bush administration critics, including Democratic presidential candidates, that the U.S. force should be reduced.
See Josh Marshall quote below.
And when you boil all this down what it comes down to is that the president now has very different interests than the country he purports to lead.