When a true Hollywood film nut asks "Why do they make B-class Horror movies?" the answer is: because people want to see them, of course.
But, why do people want to see them? The answer is quite simple:
1) Bad Acting: There is nothing better than drinking beer and watching untalented people pretend to act. This movie had some great bad actors. But, it also had some semi-decent actors. Don Maloney's character became really funny as the movie wore on (and bears an uncanny resemblance to Paul Giamatti, which may be why I thought him so hilarious).
2) Cheesy Special Effects: Fingernails growing out of fake hands. Makeup from the local Halloween store. Blood that shoots in direct squirt-gun streams. Blue screens of death. What more can you ask for? This film had it all!
3) The Plot: There's always two girls and two guys, the haunted house, and the resident paranormal expert. There are the excuses they make to keep themselves in the house (I mean, after having a severed hand feel you up in the shower, would you seriously stick around?). Again, this movie had it all.
4) Naked girls: This is probably the most important reason anyone would watch a B-movie. It's a guaranteed boob fest! I was only disappointed in that we never got to see Tammy in the buff. Oh well, there were plenty of others.
All in all, The Doorway was a great B-movie that had all the elements that us B-movie fans love.