It's sort of amazing that he's been in the background for so long.
I don't really think he's that great, so I'm actually not surprised he's been in the background. He was showcased well on Idol as a performer, and then there was all the pimpage. But post-Idol, it's been a different story. I don't know if anyone else has noticed, but while he gets all the press, he hasn't actually done much that can be seen as successful performing since the Idol tour ended.
People (especially Adam) are trying to put the AMAs thing behind him, but I'm pretty sure that hurt him a lot and the repercussions are still being felt. I think it made him seem like a niche performer, at least, one who can't appeal to the mainstream with the kind of thing he apparently really wants to do. A lot of this red carpet stuff, the hosting of the Jingle Balls, etc., are the kinds of gigs Adam is able to get, currently. If he were able to get better gigs, he wouldn't be doing this stuff. For all I know there may still be a big demand for his singing, but if so, why isn't he singing?