Who knows? But let me offer this up as a potential explanation.
Maybe he was a good locker room presence and offered NFL experience to some of the younger players in the room. But the time has come when "camp bodies" start getting cut. Tebow was simply a camp body, but with added interest, merchandise sales and of course, hope.
But like I said, this is the time for camp bodies to be cut. After his performance in the preseason game, would he continue to be a positive locker room presence? Now is when players start questioning "why is THIS guy still here?" At some point that will rub players the wrong way.
His usefulness to the team has been thoroughly used up, IMO. IMO they actually did a good job of maximizing what he was likely to offer.