Here's why:
* The anime follows its own storyline: The anime doesn't always directly follow the games, and often changes events, introduces original characters, and features storylines that diverge from the main game plots.
* N's story is already concluded: N's story was primarily focused in the Pokemon Black and White games and their sequels. He has not been a major character in any subsequent games.
* Anime appearances are unpredictable: While some characters from the games have made appearances in the anime, there is no guarantee that N will ever appear.
It's important to remember: The Pokemon anime is a continuous story that often introduces new characters and storylines. While N's appearance is possible, it is not confirmed and there is no official indication of it happening at this time.