In 1975, Laura Mulvey agued that women are used in films as, "erotic objects of desire for the males in the narrative and the males in the audience." (Mulvey 1975)
Why do stereotypes work? Because they sell the product and represent the needs of the audience who want to be entertained (Blummer and Katz 1973)
An example of these stereotypes is Captain America: The First Avenger.
In the movie trailer, you see the Character Peggy Carter - played by Hayley Atwell - as a strong, independent woman who fights in the second World War, but you also see her as a love interest for Steve Roggers - Played by Chris Evans - which does support the theory that women are used as objects of desire for men in the movie, however at the end of the trailer she is seen as saving Steve from a hydra agent and breaks the gender stereotypes as she is now being the 'hero'. However in the movie there is a few scenes which support this theory, one of them is portraying a woman as an erotic object who's only purpose is to love Steve, or another is a musical number with women wearing little clothing to attract the males and this is clear evidence as to when they perform in front of a large group of soldiers and after Steve makes a speech, one man in the crowd shouts "Bring back the girls!" as the rest of the crowd cheer while the women walk back on stage.
Evidence for the theory about men dominating action with violence is pretty much then entire movie. All of the men are in the war and fight each other, whether it is with guns and explosions or just physical violence, all of the men are fighting to create action and attract the audience. Also Chris Evans being the alpha male is shown because he is attractive and muscular and part of the main action, there is also a scene where he is seen shirtless to show his body and how physically fit he is.
These stereotypes work because they attract a specific audience such as men and some women because of the attractive male actors.