Songfacts®:

• According to the album liner notes, this was vaguely inspired by an Otis Spann number. Although it is in Blues format the verses are 14 bars long and the guitar solo verses 17 bars long. The song has a slightly humorous theme and features some fine soloing by Ritchie Blackmore.
  
  That being said, humor can sometimes be black indeed. In a May 2003 interview, Derek Lawrence, who produced the eponymous Third Album, replied to a question by Drew W of Florida in the following terms:
  
  "Can you remember any humorous stories from the early sessions that produced the first three albums?"
  
  "I do remember that the boys went to see Rosemary's Baby at the cinema and came back and wrote "Why Didn't Rosemary'"
  
  This is a reference to the lyric, for example: "Why didn't Rosemary ever take the pill?"
  
  Rosemary's Baby is a contemporary horror film based on the 1967 Ira Levin novel of the same name in which the unfortunate Rosemary played by the actress Mia Farrow is impregnated by the Devil. Directed by Roman Polanski, the film picked up an Academy Award for Best Supporting Actress, a host of other awards and nominations, and became a popular culture reference. >>>

  Suggestion credit:
  Alexander - London, England