Here's why:
* Abstract nouns represent concepts, qualities, or ideas that cannot be touched or seen. Politeness is a quality or behavior that is intangible.
* We can't hold "politeness" in our hands or see it with our eyes. It's a concept that exists in our minds.
Example:
* "He showed great politeness to his guests."
In this sentence, "politeness" refers to the quality of being polite.
Note: "Polite" can also be an adjective, describing someone or something.