Could you perform better if your pay and/or perks were multiplied?
Not worrying about money and perks makes it easier to focus. Plus think about recruiting and the rest of the team. "You're thinking about Washington? Well, come here to USC, and my agent can get you get hooked up with cash and whatever you need. Come block for me here."
Obviously not the same as PEDs, but it's a murky area where advantage could accrue (and it's almost impossible to prove either way), so they imposed a bright-line rule.
He broke that rule knowingly. Other players forewent payments because they chose to follow those rules.
Even if you think there was no advantage, should the rule breaking be ignored? If the best student in the class cheats on the final exam, should the cheating be ignored since he was the best student anyway?