Entertainment Film have numerous types of sterotypes inside their structure and their messages.
Discourse from hollywood doesn't change so often. The no variation is a good weapon to drive audiences. Entertainment spectator always knows the discourse he'll find inside the theater.
About the stories, we have a similar situation, we pick 4 or 5 themes for a season, and lets ride that wave. Is a bit like in marketing theory of the FIVE ones. People always remembers the 5 brands of a type of product. The marketeer job, is to include his brand into this range. So the same happens in stories of hollywood, we have for example: teenage suspense, teenage comedy, teenage drama, teenage action and classic thirties drama.
The only thing spectator doesn't know, is what is going to happens next