Here's why:
* Lugia's catch rate is relatively high. While it's still a legendary Pokémon, its catch rate is much higher than some others.
* You can use other strategies. You can use Ultra Balls, Timer Balls (if the battle drags on), and even regular Poké Balls with careful weakening and status effects.
* The Master Ball is meant for a single, guaranteed catch. You'll want to save it for a Pokémon you're having trouble with or a Pokémon you absolutely don't want to risk missing.
How to catch Lugia in Pokemon HeartGold:
1. Go to the Whirl Islands. Lugia is located in the Whirl Islands after you've completed the main story.
2. Prepare your team. Lugia is a Psychic/Flying type, so bring strong Dark, Electric, Ghost, or Rock types.
3. Weaken Lugia. Lower Lugia's HP and try to inflict status conditions like Sleep, Paralyze, or Freeze.
4. Use your best Poké Balls. Ultra Balls are your best bet, but Timer Balls can be effective if the battle goes on long enough.
5. Good luck! With some strategy and patience, you can catch Lugia without using the Master Ball.