There are 32 teams in the league, many are desperate for good players. Apparently, none want Tebow at the moment. It isn't because he's a Christian. He isn't being blackballed. The NFL is a violent sport where every player is one hit away from a career ending injury. That is one reason there are LOTS of outspoken Christians in the league. If teams felt Tebow could add value, they'd grab him up as fast as possible. Apparently the Jets couldn't find a single team that wanted to trade for him.
Tebow probably isn't a starting caliber quarterback - at least from what teams see on tape and hear from those who've played/coached around him. If Tebow is willing (and happy) to be a backup somewhere and maybe play TE in some packages, he may get picked up.
And that's likely why teams aren't interested in making a lot of adjustments for a running lefty QB. They want players that will fit into existing schemes so that if one goes down, a replacement can be quickly called up. Think of the risk of redesigning a team to accommodate a QB like Tebow... a guy whose career may end on the next play.