I initially thought the same. However, they're really there. You just have to be very close to see them. Beyond a couple hundred yards, the tracer just vanishes into thin air and you see no hit sprites. But if you're closer to the target, you see the tracer all th way and the hit sprites.
I imagine this probably has something to do with the graphics settings that make other objects disappear to help FPS. Also, the main gun tracer doesn't leave a smoke trail like in AH1, so it's harder to notice. All you have is the light on the shell itself. If you're zoomed in tight on a target a long way away, your field of view is too narrow to see the tracer during the brief time it's close enough to be seen at all.
