Maybe they're just keeping it like this until the community builds up, then they'll make separate mode playlists. In Black Ops, when I first got it, there were a lot of modes that I wanted to play but couldn't because it wasn't popular. So maybe Conduit 2 benefits from it's current playlists, and they're planning to open up more playlists later on.
3DS FC: 2535-3653-9390 "There are no lost causes, only lost confidence." -Monster Hunter Village Chief