Because CF is still ridiculously expensive. It's cheaper now to make than before and you might see it around more often, but it's still an exotic material. Otherwise, we would see it everywhere.
I always thought that carbon fiber weaving was not widespread and thus that was one factor in the high cost of carbon fiber. For example when Lexus was building their LFA car they also built their own 3D CF loom. http://www.youtube.com/watch?v=ry9uiP2I6kQ
Typically though you don't custom-weave CF into the product shape; you buy CF cloth and lay it into a mold. I think, though, that a lot of composite layup is still done by hand since it is not as easy to automate as a lot of metalworking processes are.
