Because monsters are important, Eli Roth will soon adapt the Grindhouse original trailer "Thanksgiving" into a feature-length film. Roth says he's working on the script now, which is to say he's thinking of new ways to kill women through their genitals.
Outside of mimicking the B-movie tradition of short, instantly-gratifying double features, there's another reason why Grindhouse was split into two different movies; rapid-fire gore about the same dumb story wears you out. And we all know he'll clock about ten minutes of story time before someone gets it, Thanksgiving-style, in the genitals. Ugh.