Business Insider have published an insightful article on the creation of PG-13 certificate in the US purely to bridge the gap that Spielberg saw while making Indiana Jones and the Temple of Doom.
Of all the films in the Indiana Jones series, there’s no doubt that 1984’s PG-rated “Indiana Jones and the Temple of Doom” is the darkest.
As producer George Lucas explained to Empire, “Part of it was I was going through a divorce, Steven had just broken up, and we were not in a good mood. It ended up darker than we thought it would be. Once we got out of our bad moods … we kind of looked at it and went, ‘Mmmmm, we certainly took it to the extreme.'”
Films like “Temple of Doom,” which were too mature for PG audiences but not mature enough for the R rating, would find themselves in limbo.
Spielberg found this “netherworld” rating unfair to both filmmakers and audiences. So, according to a 2008 interview with Vanity Fair, Spielberg says he came up with a new rating that would bridge the gap
Read more at BusinessInsider.