The developers of Runbow explain why the 3DS version of the game will be missing some features that the Wii U version originally included in the previous release. Among the reasons why, the folks at 13AM Games explain that Runbow Pocket does not feature local multiplayer do to the fact that they wanted to incorporate online multiplayer to be playable any time with an internet connection as opposed to needing to be next to each other.
The full interview can be found here, additionally, a tidbit of it can be found below:
It was basically one or another if they wanted to do that, which of course also led to no StreetPass functionality. The team wanted to preserve as much from the Wii U version, and due to the Nintendo 3DS constraints, this was one of the problems the team had to cut.
We’re one of the first teams to bring a Unity title to New 3DS. We already faced a few challenges scaling down the game to fit the full Runbow experience, single player and all, into a smaller machine, and on top of that adding different types of networking to our already complex netcode was a risk that we were not comfortable taking. We were left with a choice: Use the online system we already have in place, something that we know works and is fun, or uproot the code and build it for local features instead, while these features were still being added to the Unity engine. The latter option produced an unknowable: how long would this take us? Will it work? How many New 3DS owners are friends with New 3DS owners in the same square mile? Unity has done a great job in helping us with whatever direction we wanted to go, but at the end of the day we thought it was of greater value to our players to give them an online experience where they can play with anyone, anywhere in the world, just like the original Runbow.
Instead of having to find other New 3DS owners, you and your friends can jump into an online game of Runbow anywhere there is a wi-fi connection. Because of this, we also had to forgo the StreetPass features. We know this comes as a bit of a bummer to our fans, but at the end of the day it was important to us to preserve as much of the original Runbow experience as possible. From our massive single player campaign to those wild online matches with anyone in the world.