Here's why:
* No Official Events: Unlike some other Pokemon games, there were no official events or distribution methods for Celebi in Pokemon HeartGold.
* No In-game Method: There's no in-game way to obtain Celebi through regular gameplay.
To obtain Celebi in HeartGold, you would need to:
* Transfer from a previous game: If you have a Celebi from a previous game (like Pokemon Gold/Silver or Crystal), you can transfer it to HeartGold using the Poke Transporter.
* Use an Action Replay or similar device: These devices can allow you to cheat and insert Celebi into your game, but it's not an official or recommended method.
It's important to note that using these devices can potentially corrupt your save data or cause issues with online play, so proceed with caution.