1. Don't need more yards
2. Difficulty in controlling height and spin on the ball with GI irons
3. GI Offset might cause better players issues
4. Fatter soles may not interact with the turf in the manner a better player desires
5. Lack of feedback disguises misses
A better question would be why would a better player, who is presumably a consistent ball-striker, want to play a GI iron? Frankly, I wouldn't want a 30 yard gap from my PW to my GW or GW to SW/LW. 165 yards is plenty for a 7i, for my game.