I have these reasons in my mind:
1. EA doesn't want other game companies or individuals steal their next gen 3D technology. I think it is much easier to steal the technology or doing re-engineering to get how they do it. May be PS3 and Xbox 360 have much more protection for game makers.
2. EA doesn't want pirate PC copies happen then universities students would play pirate PC copies instead of buying a real copy of Xbox 360 / PS3. Since it is much harder to make a blue-ray or whatever for Xbox 360/ PS3 even can download it with extra large space. EA does it long time ago for NCAA footaball game, so there is no PC NCAA footaball game many years.