Part of it is performance. There is more to render with a larger field of view. Another thing is that people playing on a PC will sit only two to three feet away from their monitor, whereas console players typically sit farther away from their television. A higher FOV would then make it more difficult to see.
Personally, I don't like it too high on PC actually. While it can be fun and it does have benefits in close quarter situations, it also makes it more difficult to spot distant targets.
Me goofing off with FOV 125 in Battlefield 3:
Edit: Many of the CoD games on PC do not allow you to alter the FOV and you do need an addon for that, but BO2 and other shooters let you change it in-game.