It's partly the press distrust of the military. They came to believe some big liars during Vietnam as well.
CENTCOM is the primary news source from Iraq. They run the war and the 178,000 troops and leaders under Gen. Abizaid. I ask reporters often whether they checked the CENTCOM briefings and daily logs. They prefer their sources - placed outside the Baathist Party strongholds and in the press hotel, where America's enemies can use find them...and they troll for victims with help from the socialist NGOs who want the UN to win.