There are many great R rated movies such Shawshank Redemption, The Godfather, Rain Man, Saving Private Ryan, Pretty Woman, Blazing Saddles, Die Hard, Caligula, Disclosure, The Game, etc. The fact is PG-13 movies do best at the box office, not R rated movies. Creators of movies are not aiming at a rating. There purpose is to create a movie that audiences will like. Often objectionable scenes in R rated movies that are close to being PG-13 will be edited to slide under the wire. However, some movie subject matter is simple to violent or has too much sex to make it PG-13.
For your information script writers will usually have no say when it comes to scenes in a movie unless the script writer is the creator which today is rare. They are hired to write dialog for the actors. The Director and maybe the Producer will decide on scences. Battle scenes and sex scenes involving the actors are the most difficult and expense to film.Except for Blazing Saddles, I don’t like any of those movies. Private Ryan had the semi accurate invasion scene that was nice, but little writing talent in any of them.
Ever see Gettysburg? Deadliest battle in US history. What did you see? A riderless horse running out of the smoke. Good writers don’t need to show you grapeshot blowing his body apart. The audience knows.
And Blazing Saddles - PG if rated today.
Yes, I saw Gettysburg and the riderless horse scene was very effective. Nobody needed to be told how bloody that battle was. However, all battle scenes can not be done that way. Take the movie Battle of the Bulge. The whole movie was about a single battle. The Longest Day was about a single day in numerous battles.