The Air Force is phasing out the A10 Warthog. A plane the Air Force never wanted that is used for close air support for infantry. Ever since the 1940 the Army and Air Force have been at each others throats over close air support. The Air Force wanting to focus on air superiority while the army demands control over assets for protecting and supporting troops on the ground.
Here is an interesting fact though, the Air Force has some 5500 aircraft, the Army over twice as many- 12000. In many cases, the Army's helicopters perform better in the role of CAS. But the Air Force's F16s and A10s can provide fast support or be less vulnerable against AA.
It would also seem that since the Air Force is relying more and more on drones for precision strikes, that if could afford more resources for CAF.