Here's why:
* Compound nouns are formed by combining two or more words to create a new word. Examples include "fireplace," "sunbeam," and "high school."
* "Aunt Doty" is simply a proper noun, meaning it's a specific name for a person. It's not formed by combining two separate words.
Think of it like this: "Aunt" is a title, and "Doty" is her name. While they are used together, they don't create a new, single word.