Simple...the USAF brass hates the A-10...period, dot...yes, real people love it and it just keeps proving itself (dont start flaming, I love the A-10, let us talk about fast mover politics and getting away from an Army support role)...so no way the post-modern USAF will pay $ to keep fulfilling a mission it feels it should not have to do, especially since the Army basically tried to force the USAF to keep doing it in a manner of speaking by abandoning their Comanche project.
Nothing does CAS or FAC-A better than a Hawg...nothing...but those arent priority missions for a USAF that cant field sufficient numbers of F-22A...and if you read another post, you will see that nearly the entire USAF fleet has some potentially crippling issues.
Focus, it is not about what is best for the job, it is about what we can pay for, priorities, and politics...if the Army wants a CAS bird so bad, they can help pay for it, Airmen dont need CAS (Sandy's, yes, CAS, no) but bullet catchers do