What is an author's reason for creating a particular work?

authors write to entertain their viewers. They can write to make a clear purpose like to inform narrate entertain or explain. For example Percy Jackson and the olypian's author, rick riordan, wrote the book to entertain books like weather are made to inform and a book like how to fish is to explain how to fish. A kid can write a story to narrate not neccesarily only authors write