HappySqurriel on 21 October 2012
Honestly, I think it is because (while Sony and Microsoft are focused on competitive online multiplayer games) Nintendo is more focused on single player and local multiplayer gamers. Nintendo's big push for online services this generation seems to be designed to provide interaction between gamers even if they're playing at different times, and seems like a good enhancement to single player and local multiplayer games.
Cross game chat is (probably) a great way to invite a friend to play an online competitive multiplayer game with you, but that really isn't what Nintendo is focused on.
With that said, I wouldn't be surprised if there is a way for Nintendo to add it in a later update if there is demand from developers and gamers.
