The original reason for the Q&A system was simply to have a way to mark "questions" that had been truly answered as such, vs those that hadn't. I felt that it was something nice to have, and it was part of the many features implemented to avoid using brackets, like [solved].
Yet, like you said, every single thread here, one way or another is a discussion, and that's the cool thing about having a forum.
Originally I thought the bringing of the answer up was a good feature, it meant that you didn't have to scroll in order to get to the answer, but I see your point, maybe this needs some revision.
I'm curious on what others will think.