It's PG-13

This article explains why and how ShojoPrettyCure! Is rated PG-13/14/13+.

It is a work in progress

It was never made for children
The author CureNa11, created this fan fiction specially aimed at TEEN girls. Not 9 year olds. She decided to add things that would easily confuse/upset children younger than 12. She wanted to make it madokamagica/sailormon like, and added topics and scenarios not suitable for younger audiences, such as death, virginity, suicide, homosexuality, murder, the list goes on and on..

Besides, why not add more ADULT topics to a pretty cure series? Teens and adults also need interesting things to watch/read, especially in magical girl anime and manga, aimed at young girls "young" girls. But anyway, why not create something for older girls?