In a prisoners dilemma like set up, if any airline unilaterally changed their rules for pilots and crews, they would "lose out" when they didn't have crews to fly, while other airlines would "win more" by overworking their flight crews. The only "win" was for all airlines to not implement these changes.
But when the changes were forced on everyone, it removed the advantage of not following the guidelines (well it added a criminal or civil prosecution risk) and so all airlines have at least minimally rested crews.
That message seems to get lost sometimes.