Zips are no good, because they need to be able to link to one file only for embedding and downloading, apparently opening a zip is too complicated for sponsors :S lol. I'm guessing this is just a relic of the fact its primarily a flash marketplace. You can wrap an entire game in a .swf file, so it's both self-contained, but immediately usable for sponsors.
interesting link, I'll investigate it more and report back for everyone
Thanks for the replies!