The 1982 film Tron didn't get an Oscar nomination because the Academy
thought the movie "cheated by using computers."

The 1982 film Tron was popular for its light cycle scene created by the use
of computer technology. The motorcycles in the film were designed by Syd
Mead, a famed concept artist. Although the film's use of special effects
was new for its time, it did not receive an Oscar nomination. According to
Tron director Steven Lisberger, the film did not receive any nominations
because the Academy believed they had "cheated by using computers." Tron
was one of the first major productions to use a considerable amount of
computer-generated imagery.