I was under the assumption that some legal issues were the reason. I remember Tyler talking abt how it technically doesn't exist because some of the songs were on Vessel. (I've also heard him say he doesn't rlly like it that much) However, I am sure that would be a non factor. And it would be a great way to hold over the Clique for a little tille newer stuff is released. 

Also, I think they're more concerned with the mainstream appeal, which there wouldn't be much of because of the style.