Here's why:
* GTS limitations: The Global Trade System (GTS) in Pokemon Diamond only allows you to trade Pokemon with other players. It doesn't allow you to trade with NPCs or receive specific Pokemon requests.
* Legendary Pokemon rarity: Legendary Pokemon are incredibly rare in the game and are typically obtained through specific events, locations, or story progression. They are not available for regular trading.
To obtain Legendary Pokemon in Pokemon Diamond, you'll need to:
* Complete specific events: Some events might allow you to obtain Legendary Pokemon, but these are often limited-time events.
* Find them in specific locations: Some Legendary Pokemon can be found in rare locations after completing certain parts of the game.
* Trade with other players: Trading with other players is the most common way to obtain Legendary Pokemon. However, you'll need to find someone willing to trade their Legendary Pokemon with you.
Remember that trading with other players can be risky, so be cautious and only trade with trusted sources.