Is it generally permitted in National Forests? If so, then the prohibition in National Parks seems totally reasonable.

Drone flying is a fundamentally antisocial activity. If you're doing it far away from others then that's fine, but I have no sympathy for the drone pilots in this thread complaining that they're forbidden from flying over crowded city streets or in similar scenarios. National Parks have tons of people in them, while National Forests are generally rather empty. Those are better locations for drone pilots.