The Vietnam War was a chance to burn off the WW II surplus ordnance and keep the Baby Boomers off the labor market. When those goals were accomplished and the war looked like a mid-term political disaster for Nixon's second term, it was over, or rather, reduced to a political vendetta called the Drug War.
The war in Iraq was about contracts, munitions sales, and making George Bush a war hero and dictator. Mission accomplished, except for that "hero" part. The war that our war economy and the Republicans need doesn't need to be in any specific place. Time to 'move on'.
When asked how he felt about leaving Iraq, a British trooper said "What's the fucking difference? They'll just send us off to fight some other bloody war."
And that's the bottom line.