Not that it's a bad movie, but because someone did better. Someone beated him at his own game.
Together with Robert Rodriquez he started the Grindhouse-project. Tarantino made his movie "Death Proof", while Rodriquez made "Planet Terror".
Like a said: Death Proof isn't a bad movie, but Planet Terror is just so awesome that Tarantino fades away in the shade of his Mexican friend.
What do you guys think? Planet Terror or Death Proof?