Evolution threatening storied positions

Back in the 1960s, USC coach John McKay was asked whether it was a good idea to have star tailback O.J. Simpson carry the football 40 or more times a game.
“Why not?” the famously funny McKay responded. “It isn’t very heavy. Besides, he doesn’t belong to a union.”
Today the football must feel like an anvil, or there must be a secret International Brotherhood of Running Backs out there. Because nobody carries it 40 times anymore. Heck, nobody carries it 30 times. Very few even carry it 25 times a game.