Your theory is that the operators don't know if they are making money? Interesting theory.
There are issues with local gen, lineman safety and regulation, same as for solar. But if there is one synchronized generator still on line the little generators stay in synch by the laws of physics. For a farmer, maintaining power at an incorrect frequency is better than no power at all. See also backup generators. You do have to be careful not to kill linemen who expect lines to be dead. This is a solved problem.
You don't lose fish to small generators on rivers that are already cut off from migration. You gain local, non migratory, fish in the pond.