Originally Posted by Landgolier

Right, but rebuilding them is not the simplest process ever, there are about 100 tiny bearings in those suckers, and you can't just stick them down with grease, you want to use heavy oil. I've done it, it's not fun. Also, you're probably only taking it off if it's shot anyway, I guess occasionally you might pull a freewheel to change gearing or replace a spoke on a LF hub, but generally it's because they're done for.