Well, the problem is that Bush's entire presidential legacy is going to based on a war he started in Iraq. If we pull out now, it's going to be seen as a failure (it already is a failure, but let's not let that get in the way). He's going to do everything he can to make sure that the war goes on to the next president, so any pullout or further losses will be pinned on the next guy.
"Well, you know, I, uh, thought I left our troops in good hands, but the pullout in '09 ensured that the militants would take over the country."