Because it's consistently, for a long long time now, one of the most popular species in the game among players of the game, and among fans of the novels based on the game, video games based on the game, settings based on the game, iconic characters based on the game, pretty much anything based on the game. That's it. That's the #1 reason to include something in the game: the people who like the game, on average, like that species. That should be a really good, really strong reason to include something in the game.