TOD:
That's an excellent question. I've also wondered why terrible movies become cult favorites.
This next statement is not meant to be a "put down" to anybody on this site. It's meant to be a serious question.
Why do people on this site, including BK, even watch these movies?
Certainly you know going in that they are crap, but you still watch them. As my wife and I say after we watch a bad movie (one that we didn't know was bad): "That's 2 hours of our lives that we will never get back."
I'm not talking about films of our youth that hold a certain nostalgia. Indeed, I still, from time to time, enjoy watching THEM, THE BEAST FROM 20,000 FATHOMS and CREATURE FROM THE BLACK LAGOON, but in their day they were quality movies of the genre...and they are still enjoyable to watch. On the other hand, a film like ROBOT MONSTER was terrible back then and is unwatchable today.
With regard to PLAN 9 FROM OUTER SPACE, which I watched on television one night at about one in the morning, had me laughing out loud because it was so inept...but I wouldn't want to see it again.
So, I guess I'm not the best one to answer this original question, but I would definitely like to hear from those of you who do enjoy watching and re-watching movies that you know are crap.
Again, no offense is intended.