Another way to look at it is that the Oculus isn't just a peripheral, it's a platform. Console makers have learned how important it is to either keep console costs down or subsidize in order to reach the largest user base, which in turn draws developers and subsequently a larger library which leads to more platform purchases.
Most titles aren't going to work with the Oculus out of the box. Even for a standard FPS you can't just check box and enable VR. The best experiences, and the ones that will drive sales will be designed specifically for VR.
Think about 3D movies and the difference between seeing something like Avatar that was created with 3D in mind and some of the terrible 3D addition cash grabs that have come out. A lot of those poor post 3D additions have turned people off to 3D movies altogether.