As is the way with most free titles, the developers need to claw back some cash any which way they can. With Runbow, that cash collection comes in the form of multiple DLC packs, with no less than.

Were you concerned about changes to the social living-room dynamic in bringing Runbow to 3DS? Depending on your circumstances on Wii U, two players might actually be tethered together by the controllers when playing this game where it’s super easy to mess with each other, which creates all sorts of interesting social situations that would be absent if everyone needs their own console unit.
Well, the way we look at it, Runbow Pocket will be a different experience from Runbow and will be experienced by a different user than Runbow.
While the multiplayer features of Runbow are obviously a huge attraction for people, the response to the game shows that most players spend the majority of their time mastering the single player story mode of the game, and trying to get Bowhemoth high scores. Nemesis of the roman empire mods. Local and Online multiplayer is great, but you might not always have a buddy around and that’s why we spent a sizeable amount of development time making Adventure, Bowhemoth and the Satura’s Space Adventure DLC.
People fell in love with the characters (especially Satura) and the collectibles in the gallery and the achievements, and we think that’s great.
So for Runbow Pocket we recognize that A) people really dig the single player stuff and B) handheld devices are often used in isolation, on a bus or on a plane – not at a party. So we want to accommodate those players with this game. For example, we are changing some of the achievements in the game to accommodate more solo play, and are using StreetPass to highlight your progress in the single player, your bowhemoth times and deathcount, etc. If you pick the game up at retail it also comes packed in with all the DLC including Satura’s Space Adventure and some other goodies as well.
So, to answer your question, we’re not really concerned about the shift in the social dynamic, and think that those who really want to have a party will enjoy the Wii U version, while those who want more of a solo adventure experience might prefer to take it on the go with Runbow Pocket!