There is a certain amount of ego gratification within the services when they "set themselves apart" from the other branches. Mostly it boils down to budget justification.
Once again I feel this is parochial nonsense. When I went in the AF, they were just phasing in the BDU uniforms. Utter waste of money and resources IMO. There was nothing wrong with the fatigues, they just weren't as new and cool looking. During my four year tenure they adapted and changed either the BDU or the Class A's no less than 4 times.
Don't get me started on their F'ed up PT test...
There was a rumor going around while I was still AD that the AF intended to remove all the A-10's from service, as there was under development an F-16 variant that utilized a 30mm rotary cannon. Once the Army got wind they offered to "buy" all the A-10's and support equipment so that they might integrate them with the Apaches. The AF went apeshit thinking that if the Army acquired fixed wing aircraft, they would try to take over the AF slowly. So the A-10's remain in service, under USAF control. While the rumor may or may not be true, it rather effectively illustrates the tribal mentality that all the branches have.