Movie studios often have unrealistic expectations when it comes to box office sales, and when a movie doesn't live up to those expectations they pull it from theaters without a second thought.
Sometimes low sales justify the pull, or in the case of The Rocky Horror Picture Show low sales plus controversy cause the movie to get pulled, but studios never know when a movie is going to become a cult classic.
Rocky Horror has gone on to become the big daddy of all cult classics- it has played continuously in theaters across the country for the last 37 years.
Movies like Office Space, Heathers and Donnie Darko did well in the rental market after becoming cult classics, because people spread the word about these offbeat films that were barely in the theaters.
John Carpenter's horror classic The Thing is arguably the most surprising box office flop, because between Kurt Russell's performance and the amazing creature fx it should have made it big.
But E.T. had come out two weeks before, and Blade Runner came out on the same day so it's possible The Thing was just overshadowed by the competition.