Teams lined up to sign Mike Vick despite the media circus, despite being out of the game, despite past questions about his ability to perform at a consistent level, even despite injury concerns because he had talent that could be useful to an NFL team. If no one is willing to sign Tebow, it isn't because of the media circus, isn't because of rust, isn't because of consistency, it is because they don't think he can be useful.
This is a cutthroat league. Teams will do anything if it means winning one more game or making people waste gameplanning time preparing for some bench player. If they aren't even willing to use a roster spot on this guy, it means he isn't useful.