Am I the only one that can't just take a funny, gory popcorn movie for what it is without demanding to know everything? Did you bitch when they didn't explain how the "virus" started in dawn of the dead too?
Dawn of the Dead was using a classic horror base, with the Comedy built into the script.
Cabin Fever was using a dumbass horror base, with the so called comedy tacked on almost as an after thought to the script.