Why? Because I just like this post from March, 2011 is why.
We like seeing official Air Force photos of Battlefield Airmen applying airmanship to the tasks at hand. In this case we see U.S. Air Force Lt. Col. Stacy Maxey, a command air mobility liaison officer with Task Force CROM, giving a landing zone safety officer course U.S. Air Force, U.S. Army, and Romanian army personnel at Forward Operating Base (FOB) Lagman, Afghanistan.
You will note the combination of AF Digital Tigerstripe, Army UCP and Army OCP (MultiCam) clothing and equipment on the Airmen in the photo. Expect this to be the norm for at least the near future as deploying Airmen transition to OCP.