Blindly telling every person who takes guitar lessons that they must learn scales, must learn to read music, must learn music theory, is a classic case of the blind leading the blind. I also thought this morning that the blanket teaching of music theory without regard for a student's needs is analogous to a dog chasing it's tail, but not nearly as cute.
I have a very good friend who studied photography in art school. She is nothing less than spectacular at it. I have been ranting a lot about music theory to her, and she offered this: "The idea that many educators have is that a person must know everything before they can touch anything." Yup. Pretty much about sums it up. And it really really bothers me. Does that mean that anyone who doesn't know something can't create with it? Also, would you even want to create anything if you already knew it all? If we listen to educators with this specific idea in mind, we wouldn't let ourselves create at all. We'd be too scared.
The long and the short of it is that I think there needs to be a period of time for someone to grow in the absence of music theory before they learn it. To paraphrase Julie Cameron, seek mystery, not mastery. As far as education goes, the question is not what to teach people, but what is appropriate to teach any specific person at any time.