It started way before "Gremlins".
Back between 1934 and 1967 up to the 1990's a rating system has been in place for films. Movies during the early life of the rating system had to adhere to "The Code" a guideline that restricted movies to Hays Codes that all movies had to meet. This is why older movies don't have what many movies today have including, excessive foul language, explicit sex or extreme violence.
The first movie to receive an R rating was "The Split"
The first movie to receive a PG-13 Rating was: Gremlins.
But what really makes the difference? How do they determine how a movie should be rated and what is the threshold of an R Rating to a PG-13 rating?
Don't blame the government for rating a movie so high or so low. You should blame your parents. Because that's who rates movies for Ratings. Eight parents assemble, Avenger style (not really), and they watch the movie and give their opinion on the movie and give the film a rating between a G and NC-17.
For a PG-13 movie, there can be violence, however it can't be persistent violence. And foul language is allowed but it can not be a derivative to be used in a sexual context, huge no no.
PG-13 ratings act as a stronger warning to parents to tell them that some material won't be okay for their pre-teen children. It's important that parents are aware of what is in the movies.
An R rating is give for movies that have the following:
- The "F" word used as a Verb
- Tobacco Use
- Hard Drugs
- Extreme Violence
To use the "F" word as a verb in a sexual context automatically gets it an R rating.
In 2007, MPAA announced that it would factor tobacco smoking into the rating of a movie. Not only that, but Universal Studios would not allow tobacco to be used in movies with a G through PG-13 rating.
For hard drugs to be used such as cocaine, heroine, or any illegal drug in movies, the movie receives a PG-13, however graphic depictions of using drugs gets slapped with an R rating (Requiem for a Dream)
Nudity is a tricky subject. Shirtless men are okay in G movies, but shirtless women get a PG-13. Fully nude men get an R but fully nude women get a PG-13. This is one of the items that has many people questioning the system.
Getting to a sadistic violence garners an R rating. Any violence in movie is okay, until it becomes sadistic or depraved, then the R rating comes in.
From this we can see that an R rating and PG-13 rating are quite different, and that R ratings are for harsher movies. However some movies have an R rating but are not as harmful as other movies, an example given is Billy Elliot compared to Saving Private Ryan, both have an R rating.