Don Simpson and Jerry Bruckheimer, who were/are producers, believed that an action movie needed a “whammy” every ten minutes or so. A “whammy” being an explosion, gunfight, crash, chase, etc. Their films were often big hits and defined action films in that era, so naturally other studio execs, producers, directors, and writers would imitate their style.
I can’t seem to find cite linking Simpson to “whammies”. All I can find is one linking director Renny Harlin to the concept. Still, I’m sure Simpson and Bruckheimer embraced the same idea.
Most screenwriters work on assignment, at the direction of producers and/or studio execs. Directors and stars also have a great deal of input once they sign on to a project, though it’s usually studios and producers who are paying the writer. Writers who aren’t giving these power players what they want will usually be replaced. It’s not unusual for a script to go through ten different writers, or more, before it finally goes into production. Of course, most scripts that are assigned and purchased never get made.
A writer who wants to work, and keep working, will try to anticipate the demands of the power players, and give them what they want, within reason. So, the writer might put in all the required whammies before hand, or any one of the power players might ask for more, or ask for different ones. Requests for changes in the script, are called “notes” and addressing these notes is a big part of the screenwriter’s job.