In a word: jobs. President Obama's latest goal of creating or saving 4 million jobs can't stand to lose the jobs created by the Iraq war. At recent count, there are 144,000 U.S. troops in Iraq and 190,000 independent contractors. Given that one third of a million people working in Iraq, between reservists, troops in training, troops currently rotated out of Iraq, defense contractors not working abroad, and 44,000 troops in Afghanistan, wars in the Middle East are easily employing 1 million people.
These jobs are essentially off the table. The administration can't claim to be saving jobs by not eliminating them, itself; the saved and created jobs need to be in the private sector--something it can't directly control--hence the focus on things like clean energy and infrastructure projects. It's between a rock and a campaign promise. Essentially, continued spending and shuffling troops is easier than adding 1 million to the already-tall order of 4 million jobs.