Well, maybe they want to make Heatran be able to use Attract.
Heatran is one of the few Legendary Pokemon with a gender and many people have wished to teach their Legendary Pokemon Attract, and they have realized it can't be done. Try putting Attract on Arceus, for example. Make it unstoppable. But you can't because it's.......drum roll.......Genderless!
But now we have Heatran who can have a male/female gender, giving you the option of totally PWNING Pokemon...who love you.