I don't collect high grades slabbed comics, so am just guessing here. I imagine many people collect the highest grade CGC books, in part for the the aesthetic appeal of a flawless collectible, and in part for the the pride of ownership of a rare item. There are other reasons for sure, but for the two reasons cited above, OA meets the rare item criteria, but not the flawless collectible criteria. Many collectors are transitioning to collecting OA, and yet the two areas of the hobby still seem almost unrelated.