M
Mjölnir
Guest
Rhodey was an active duty officer in the US Air Force as of Iron Man 3. His armor still had military serial numbers on it in CW, IIRC. Marvel has made a mistake in having Rhodes stay static at the rank of lieutenant colonel since Iron Man. An Air Force officer would have promoted several times over nine years. Failure to earn a promotion over so many years would have ended his career in the real world. In fact, there is no reason why Rhodes wouldn't be at least a brigadier general by the time of CW, given his achievements and status as a hero.
My first thoughts, which weren't very active, were that he's put there because he's still wanting to be an active soldier and moving up should move him further and further away from that (even the rank he has feels high for someone active on the front line).
At the time of Civil War he feels more like an Avenger than part of the military (which I suppose the end of AoU confirms). If he was still in the military hierarchy it seems more likely that he'd be with Ross, trying to persuade the Avengers, rather than being part of their internal discussions.
I'm not arguing against that he couldn't have been promoted though, as he's certainly a special case that's not applicable to anything relevant in our world. He seems to have gotten plenty of medals and such though, so perhaps that's how they are dealing with it.