Here's why:
* Legendary Pokémon are generally not breedable. They are unique and powerful creatures that are meant to be encountered in the wild, not created through breeding.
* There are exceptions. Some Legendary Pokémon, like the Lake Guardians (Uxie, Azelf, and Mesprit) in Pokémon Diamond, Pearl, and Platinum, can be bred. However, this is not the case for the Legendary Pokémon in Pokémon White.
If you want to obtain a Legendary Pokémon in Pokémon White, you will need to:
* Catch them in the wild. This is the most common way to acquire Legendary Pokémon.
* Trade for them. You can trade with other players to obtain Legendary Pokémon you haven't caught yet.
* Use events. Some events, like the distribution of Mythical Pokémon, allow players to receive Legendary Pokémon.
Remember, the breeding mechanics in Pokémon are specifically designed to allow players to raise and train various Pokémon, but not to create Legendary Pokémon.