12 frames per second is common in cartoons, stop-motion animations or Animes simply because it means less work. And since it is exactly 50% of 24 Frames per second, it was compatible with most cinema projectors back in the analog age.
Today, it is more used as a stylistic element to create the anime comic book style.
A good example of that is the Spider-Man Spider verse Movie series, in which the frame rate switches between 12 FPS and 24 FPS. To have the Comic Look on the onside but still make it possible, to pursue fast movements.