Why doesnt Pro Golfers use graphite shafts on tour?

They do in their drivers, fairway woods, and hybrids. Most don't use them in their irons because you want control on your iron shots and you can do that better with steel shafts. Some have used them in their irons like K.J. Choi at one time and Colin Montgomerie. You see more on the Champions Tour use graphite shafts in their irons due to the lack of club head speed.