Minun Is Not United Nations (M.I.N.U.N.)

I wonder why Pichu evolution families are absent in Unova Dex? I'm thinking Minccino as Pikachu replacement as they are rodent-based Pokémon, despite being a Normal-type Pokémon. That's very sad news for Pikachu fans because players cannot take any Pichu or Pikachu until completing main story.