Sadly, the USAF decided to retire the Hog because it is a single mission jet.
Simple.
The rationale, such as it is, is to retire single mission jets in favor of jets that are multi-mission capable.
Great idea in theory but a multi-mission jet is proof that a jet can be a jack of all trades but a master at none.
The A-10 is a master at CAS.
Budgets. Budgets. Budgets drive awful decisions sometimes, and USAF users of the A-10, from the pilots to the USAF guys on the ground (yes, the USAF has guys on the ground on the front lines in battle), they in no way want to retire the jet. . .it is the Wash DC acquisition geeks that argue for the multi-mission jet.
Try to make it a master of all and the cost per plane goes through the roof. The A-10's biggest asset is that it's cheap to buy and cheap to keep (although I would think it vulnerable to MANPAD type weapons).
I worked on OA-10s a bit back in the day...and to a man, not a one of us wished we were doing anything different, even the pilots.
For anyone who says that the USAF “hates” the A10, I’ll just be polite and say you don’t know wtf you’re talking about.
I guess a multi-mission designation somehow makes it easier to argue before congress...look at the F22 and it’s SDB modifications recently...