I think a lot of people actually believe he's a good prospect, but simply don't want to admit it. That's the only reason I can think of. Tebow has a lot of work to do, but he's a monster FF prospect. I don't see how anyone could say otherwise.
That doesn't make him a lock for success, but I like his chances for many reasons.

You can't think of a single reason someone might question Tebow's future in the NFL beyond that they really DO believe it deep down but just don't want to admit it? wtf kind of nonsense is that?
there are about 137 reasons Tebow will NEVER been a starting NFL QB for more than a few games, and they all involve his lack of skills and inability to do things like throw the ball accurately. He's NEVER been able to. how is that going to change? You are either fishing or a fool - there is no other reason for being this intractable.
You know as well as I do there's people that hate Tebow regardless of what they think of his ability. For whatever reason, he's one of those players that just evokes it. I kinda get it, NFL fans are passionate, but people should separate their like or dislike & rate players regardless of their feelings. Anyway, it simply amazes me you & others can write him off based on today's game. Like he hasn't flashed very good ability before. I find it pretty unbelieveable, lol.
That said, Tebow has a lot to learn. Bad game today, but write him off? No way. I could be wrong, sure, but the key is to be right much more than you're wrong. Long ways to go, though, IMO.
BTW, one thing a good FFer does is not be too stubborn. If it gets to the point I don't think Tebow is going to make it, I'll jump ship. FF is a fluid hobby.