Yeah, that's a good question, but my guess is that it's a pretty big move to make something to contend directly with Pokemon's main mascot. Doing it with Raichu was relatively safe territory because it's not the mascot of Pokemon that Pikachu is, whereas when it comes to Pokemon, it's Pikachu that gets stamped everywhere. So that's probably why they didn't want to give Pikachu an alternate form. And I imagine they're likely going to keep it that way.