The whole Sci-Fi thing is that, Sci-Fi. Yes, we are bringing some of those ideas into reality, but they don't function the way they do in Sci-Fi (You don't see people in Sci-Fi madly waving there arms about trying to get it to recognise they are moving, or take the correct command), and it will be cheaper to go out and do the real thing for a long time yet. Want a FPS with you as the controller? Play Paintball or Laser Skirmish. Racing game with you as the controller? Over here the local racing tracks will let you have a drive around for a small fee. Sure, you don't get the same areas as you will in games, but RL is far more immersive than any Motion controller will ever be, especially within our life span.
As to how would you sell a controller, the same way you sell a gaming mouse over a normal mouse: More responsive, faster reacting, easy adjustments that you don't have to learn actions for, you don't have to put as much effort into carrying out actions as you would otherwise, ect. There is always things that controllers with more buttons will do better. With the current technology, imagine playing an RPG and getting your character to cast the right spell. It would be horrid.
In present time, Motion Controls are a gimmick used to earn money of the 'Wow, I've seen this in Sci-Fi' mindset. If it is developed enough, it may transcend that and become a reasonable form of controller, but currently it is inferior in almost every way to conventional controllers, and I doubt the companies are doing it to push forward technology. They are run by bank checks, not well wishes for a Sci-Fi future.