You're basing this off of statistics that ignore how these negotiations happen. Or really any sort of nuance that makes a difference in the real world. Like the quality of work the individual outputs or how much the company needs them, or how well they're perceived by their peers overall, or just how smartly they approach their employer when negotiating.

"Please give me a raise" is not a negotiation. To negotiate properly you need a trump card, "please give me a raise" doesn't show one.