Why can’t you sell your Superman fan fiction? Bill Clinton!
Since the dawn of creativity, people tried to find a way to protect what was rightfully their work and ideas.
Copyright provided the perfect solution of allowing a creator to obtain some revenue for their work while allowing it to enter the public domain after some years.
However, over the last century that journey to the public domain has gotten longer and longer—and that's why you can't sell your Superman fan fiction!
Bill Clinton signed the Sonny Bono Copyright Term Extension Act in 1998 to extend the life of copyrighted material an extra 20 years, an additional fifth of a century! People looking forward to reinventing, reissuing and revive some of the most iconic works of the 20th century would have to sit on it for another significant patch of time. Maybe they can pass the idea down to their children!
If it weren't for the Sonny Bono Copyright Term Extension Act of 1998, Superman would have entered the public domain on January 1, 2014. That would have been really bizarre, especially since the Man of Steel continues to be in contemporary pop culture and big blockbuster movies!