One of my pet peeves is when a reviewer will automatically compare either two books, movies, actors, etc just to get name recognition. Several years ago when I was a pre-teen and still reading fantasy, all of the books would say something like "for fans of Harry Potter". More recently it has been with "for fans of Twilight" or "fans of Hunger Games looking for something to read need search no further." Even when I was 12 I thought this was odd because generally the books had nothing to do with each other except perhaps the genre.
More recently this has bugged me with actors. For example comparing Shirley Temple to Mary Pickford when in reality they were completely different. But the one that really gets me is all the attempts to compare whoever to Marilyn Monroe. For example a review of David Stenn's wonderful biography of Clara Bow contains the phrase that she "was the Marilyn Monroe of her day."
Wait, what? Now if you have seen a smidgen of either's work you would know they have a completely different style, partly because talkies and silents require a vastly different acting technique. Also their images are different. Monroe is the stereotypical, generally passive, dumb blonde sex symbol (at least in her movies). Bow is nothing of the sort. She is vivacious and generally is very active in getting her man. Clara plays working girls, but not simpletons. Part of this is that they come from completely different decades. Clara Bow is the perfect liberated female of the 1920s, while Monroe is really a naive sex symbol well suited to the far more conservative 1950s. (Note I do like Monroe, but personally I like Clara a whole lot more and think she is more talented.)
But you say, perhaps they are referring to their similarly tragic personal lives? Well, "Runnin' Wild" points out that Marilyn often exaggerated her childhood woes to get sympathy. Bow may have talked about her life, but it was not to get sympathy. She was just honest about where she had come from and didn't care what others thought. Now Monroe didn't have a great personal life, with foster homes, etc; but frankly I can't think of a life much worse than Bow's. While Marilyn was in decent foster homes, Clara was nearly killed by her schizophrenic mother and raped by her alcoholic father. One of the real tragedies of Bow's life, I think, is that she married a nice guy and had two sons, but was unable to care for them, even though she desperately wanted to, because of her terrible mental health caused by her awful childhood and a family history of schizophrenia and other mental illnesses.
Lastly although Clara Bow had a terrible insomnia, she was rightly known as "the hardest working girl in Hollywood" because of her work days that often lasted eighteen hours (six days a week). As we all know, Monroe was rarely punctual, driving her coworkers crazy. Clara would never have done this.
Really the only similarity that I can think of is that they were both sex symbols, so not surprisingly the name check is pointless. Also I can't imagine it would sell more books. Like there was anyone in a bookstore thinking, "Uh a book about an actress I never heard of", flips over book, "WHAT? she was like Marilyn Monroe? I am now buying ten books for each family member and his dog." Honestly name checking could work with fantasy directed at pre-teens, but why do it in this case?