The reason? He doesn't want to make a movie worse than "Death Proof."
"Death Proof," of course, was the Tarantino contribution to the experimental 2007 effort "Grindhouse," which paired the shock flick with Robert Rodriguez's "Planet Terror." Tarantino's half featured Kurt Russell as a stunt man serial killer who murders hot women by intentionally crashing his car while they are passengers. Okay, so "Death Proof" isn't exactly a great film, but over the past five years it has picked up a bit of a cult following.