I think because CGC didn't have slabs for them till now. Next they need to do is Treasury Size and all will be right in the world ----------
slabbed magazines are of an unmanageable size. i have no problem with regular size magazines as they fit just fine in a magazine size box, which most comic shops tend to carry because many GA books and some SA doesn't fit in a regular box anyway. i prefer magazine boxes.
Here are two of my favorite foreign issues in a sequence together. The one on the left is German issue #83. The one on the right is Argentina #1. (This cover concept was based on a Mad article that showed the aftermath of various Mad covers -- I can't remember which issue this was, but it fascinated me when I was a kid, and I longed to enter an alternative reality where such issues existed. Little did I know, they did in fact exist with foreign issues.)