The real answer, from a business standpoint, is that he's been out of the league for over a year, and therefore isn't an active member of the NBAPA. 2K has a contract with the NBAPA to use al of its players' likenesses in the game. To get a guy like Iverson in the game they'd have to contract him independently, which they've decided isn't worth the extra money. I'm sure that, if 2K could, they'd have every player that's ever been in the game but not officially retired in the free agents list, but they can't do it. This is the same reason why Barry Bonds wasnt in any baseball games for years, and neither were the 1994 "scab" players like Kevin Millar because none of them were MLBPA members. I have fond memories of manually renaming all those guys back in the day.