I think if you go to any of the websites selling high quality components you will find almost as many high quality graphite iron shafts listed as graphite driver shafts. Pretty much every company that makes high quality graphite driver shafts also make graphite fairway wood, hybrid and iron shafts too.

I think the reason you don't see them advertised as much to the mass consumers (although I see them advertised all the time in the clubmaker ads I receive) is because most consumers don't care so much about iron shafts once they've bought their irons. From the general discussion on this and a few other golf forums I've seen it appears that re-shafting drivers is a lot more common than re-shafting irons.