I will never, ever understand NRS's thinking process. MKX's entire roster is still a complete mystery to me. It makes no sense in how the story plays out. It's like:
"Well these characters play a very small role in the story and these characters play a larger role in the story. Eh... Lets take the smaller roles, give those characters roster spots and keep the others as NPC fights. Cause reasons and such."
And honestly, if the reason is "fan service" I find that to be incredibly weak. MK has survived without the inclusion of Kang, Lao and Kitana before. And so long as Scorpion and Sub Zero are made available within the game, I really don't see anyone (sane) having severe mental break downs over their favorites not being involved with a game. I understand the "what if" aspect of those characters, but lets be honest... That would have been better for a DLC pack rather than the launch game.
Despite how much I adore MKX - It will always be that one game with the most confusing roster in the entire series. And that's with games like MKIII and MK vs DC.