I believe I can answer that Kaje... it is to prevent accidental posting, and thus allow for a cleaner forum and less work for the staff in removing those accidental posts.
I appreciate your point of view. I kind of miss just being able to type a reply straight away, but it's much more of a headache deleting posts made in mistake than it is to click one of the reply icons.
And less work cleaning up the forum means that staff can spend more time answering members' tech questions.