Beats me. I don't know the secret origins of Keyblades or anything, but the key look's not just for show. They can open any lock, seal the hearts of worlds from the darkness... If you can get past the idea of a key as a weapon, they're actually a pretty big deal.

[In more ways than one, but there's a lot of finer details he hasn't even brushed upon yet. The whole Mark of Mastery business comes to mind.]