It levels the playing field a lot and they aren't pleased with that.
The amount of money "invested" in college sports is finite. The "sponsors" of NIL deals are just shifting their "contributions" from the institutions to the players. And that is what guys like Day and Saban are upset about: their loss of control.
These are the same guys that whine about the transfer portal. No longer do they get to chose who leaves when they recruit over a player.