Here's why:
* Fiction is categorized by genre: Fiction books are categorized by genre (e.g., mystery, romance, science fiction) rather than by subject matter.
* DDC focuses on factual information: The DDC is designed to organize and locate factual information.
* Fiction is creative: Fiction is creative writing and doesn't fit neatly into the categories of the DDC.
Example:
* Nonfiction: A book about the history of the United States would have a DDC number like 973.
* Fiction: A novel about a detective solving a murder wouldn't have a DDC number because it's a fictional story.
Therefore, fiction books are typically categorized by genre or author, and the DDC is not used for them.