I personally enjoy having my well-established expectations shattered, as the changing (from the book) of the solution to the crime in Rising Sun, or the gone-useless female in Night of the Living Dead becoming the gutsy survivor in that movie's remake, or the almost-irrelevant love interest in the Manchurian Candidate turning out to be a very relevant player in the remake.
shareIf Janet Leigh in the original had absolutely nothing to do with the brainwashing/assassination plot, she´d pretty much be ´totally´ irrelevant. Or maybe she was as some kind of a satirical red herring thrown in as a parody of a standard movie romances struck up in the unlikeliest places at the unlikeliest times (the totally nuts conversation they have on the train kinda supports this interpretation I guess). Which would still render her sort of irrelevant.
"facts are stupid things" - Ronald Reagan