Why are there not as many princess diary movies as there are books?

The disparity between the number of "Princess Diaries" books and movies largely stems from the nature of film adaptations, which often condense or simplify source material to fit a specific runtime and audience appeal. While the book series by Meg Cabot has multiple installments, filmmakers may choose to focus on a select few stories that can be effectively translated to screen. Additionally, the success of the first two movies has made it challenging to develop new content that meets fan expectations without diluting the original charm. Thus, studiOS may prioritize quality over quantity when it comes to adaptations.