Here's why:
* Game Content: Pokemon Mystery Dungeon games typically feature a limited pool of Pokemon that are available to join your team. This is due to story and gameplay constraints.
* Legendary Pokemon: Legendary Pokemon are often reserved for special events, later installments of the series, or are not available in certain game versions.
Here are some ways to get Legendary Pokemon in other Pokemon Mystery Dungeon games:
* Special Events: Nintendo sometimes holds events where players can get access to Legendary Pokemon through special codes or in-game events.
* Later Games: Pokemon Mystery Dungeon: Explorers of Sky, for example, allows you to encounter some Legendary Pokemon through the post-game content.
* Trading: If you have access to other Pokemon Mystery Dungeon games, you can trade with players who have Legendary Pokemon.
Unfortunately, there's no known method to get Articuno in Pokemon Mystery Dungeon Blue Rescue Team.