Many of you are going to go "Why would you play an FPS with a controller?".
The answer is simple:
1. In the beginning FPS games were on "Consoles", Not PC's. Despite the fact that many prefer a mouse and a keyboard these days, controller give you an infinitely superior advantage in response times, as well speed of action and aiming.
With games which have proper support for them, a controller is ALWAYS superior to the mouse and keyboard.
2. Many prefer the controller because of comfort-ability. Even in games which offer no support for them, Hence they use Xpadder to link their keyboards with their controllers.
3. A game like this will be desired by many, and as far as finances and profits go, why only cater to some, and lose profits, when you could add controller support and cater to all types of players and increase your profits? Because there are 1000's and 10's of 1000's of players that will simply chose not to play this game because it lacks Full controller support.