EDIT: I ramble here, so read at your own peril.
Each additional point is harder to get because you receive more defensive attention. So, he might only score 6 more points a game, but how much does his added offense decrease the burden on those around him. If his offense accounts to 3 additional points a game compared to Hayes (or some other player), no matter if he is the shooter or someone else on the team, then those 3 additional points can have a huge affect on wins/losses over the course of a season. Imagine a team that averages 98ppg and one that averages 101ppg. The 101 team is more likely to win more games. Of course if the 98ppg team is great defensively and can cause the opposing team to score 4ppg less than the 101ppg team can force, than that offsets any increase in offense and the lower scoring team would be better.