Plenty of great horror movies would have been even more frightening, unnerving, and effective had they received the strict adult-only R-rating. While PG-13 movies have the potential to explore some gruesome and terrifying concepts, filmmakers are limited in how much gore they show or how depraved the psychological torment their characters experience can be. Although all these horror movies had their scary moments, an R rating would have allowed them to take extra steps in the realm of overwhelming terror.

https://screenrant.com/pg13-horror-movies-benefited-from-r-rating/