Tebow played for what, 3 or 4 teams? And none of them found him worthy of keeping around as a backup. Ultimately, if a team thought he could help him win they would have brought him in. And it certainly didn't help him how rabid his fanbase is. Literally the last thing a team wants in a backup QB is someone who (even if it's through no control of their own) is going to be a distraction.