Perhaps because one could say the "twist" isn't really what the film is about, and that the ending doesn't really give an easy answer to the preceding questions?
The Thing Halloween The Shining The Evil Dead Creepshow Dawn Of The Dead Day Of The Dead Night Of The Creeps My Bloody Valentine Friday 13th The Sentinel Cannibal Holocaust
The Descent. A great dual-meaning, and surprisingly, not the original title. "The Dark," was the original title, and the one they picked is much more meaningful for the film. I haven't seen it, but Twitch of the Death Nerve just has a great ring to it. Friday the 13th: The Final Chapter.
Here's a list of titles that have not been said yet, that I think are rad: Bloodsuckers From Outer Space. I Was A Teenage Zombie. 2000 Maniacs. Dead-Alive. The Alligator People. Bad Taste. Tombs of the Blind Dead. Bio Zombie. Chopping Mall. The Crazies. Evilspeak. Deathdream. Motel Hell. Dust Devil. Frankenfish. Nightmare City. From Dusk Till Dawn. House of 1000 Corpses. The Devil's Rejects. It's Alive! It's Alive 2: It Lives Again. It's Alive 3: Island of the Alive. Jason Goes To Hell. Killer Klowns From Outer Space. Kingdom of the Spiders. Maniac Cop. Phantasm. Poltergeist. Prince of Darkness. Rosemary's Baby. Scars of Dracula. Shock Waves. Silent Night, Deadly Night. Silent Night, Bloody Night. Memorial Valley Massacre. It Happened at Nightmare Inn. Street Trash. Two Evil Eyes. Vampyros Lesbos. Video Violence. Videodrome. A Blade in the Dark. Daughters of Darkness. Night of the Lepus. Igor and the Lunatics. Surf Nazis Must Die!
Many good ones already mentioned, like MAKE THE DIE SLOWLY, I SPIT ON YOUR GRAVE, SHRIEK OF THE MUTILATED, NUDE FOR SATAN... How about FERTILIZE THE BLASPHEMING BOMBSHELL...
The ending fits in with one of my main beliefs about the life experience, so I found it more expected and affirming in my view of it, as strange as that sounds. I could see how it could unsettle some viewers though. Great execution whichever way one looks at it, yes?