According to the UN report, allies killed more afghans than insurgents, why trump administration dont get it and admit their flaw?

I don’t get why the Trump administration can’t pull the U.S. out of both Afghanistan and Iraq and end the war. There is no other reason to be there. The main target has been dead for several years now and Al Qaeda is no longer a threat. And the Taliban is not even close to a threat for the U.S. to be staying there either.