Um...because how we teach should reflect how we learn, which in turn should reflect what we know about neurology and learning? Why should we NOT start a conversation about pedagogy in aikido in a forum on teaching aikido?
Perhaps I was insufficiently clear, Janet. Let me try again. "Why is this a thing" means simply "Why is this something to be concerned about", and the question mark at the end means that it is a question. As for "what we know about neurology and learning", this is the first mention of neurology in this thread. If this truly is a "neurology" thing, I'd be interested to hear more -- otherwise, it really seems like purely a matter of personal preference to me (and it's pretty hard to distinguish preference from functional advantage).