Here's why:
* Eevee is a Johto Pokémon: Eevee is native to the Johto region, which is where SoulSilver takes place.
* No Eevee in Kanto: While you can transfer Pokémon from Johto to Kanto in SoulSilver, there are no Eevee encounters available in the Kanto region itself.
How to get Eevee in SoulSilver:
1. Catch an Eevee in Johto: You'll find Eevee in various locations in Johto, particularly in the Ilex Forest and the National Park.
2. Trade to Kanto: Once you've caught an Eevee in Johto, you can trade it to your Kanto version of SoulSilver.
3. Breed for More: If you want more Eevee, you can breed the one you caught or traded.
Remember, you can't find Eevee in the wild in Kanto in SoulSilver, so make sure you catch it in Johto first.