Because every console needs an iteration of Mass Effect, even if it's just the third one.
After two games in the series missed appearances on Nintendo systems, Mass Effect 3 is now making its way to Wii U.
In Mass Effect 3, you take the role of Commander Shepard, a character players can either customize to be any gender, race, and size, or leave in a default male or female appearance. The game is a combination of action-RPG elements and more traditional third-person shooting. It includes character leveling, plenty of skill tree options, many different combat skills to alter to the player's specifications, and a story with emotional heft.
The story finds Commander Shepard as he or she (and earth) are attacked by the ancient Reaper alien race, after Shepard had warned everyone, to no avail, that such an attack would be coming. After the chaotic invasion, Shepard is tasked with forming alliances across the galaxy to build an army strong enough to save organic life as we know it.
One of the most interesting things about the story of Mass Effect 3 is how it gives the players the option of how to react at every turn in the story, allowing the game to build a personalized experience around the player, and even change the path of the story based on past actions and choices.
Because so little was shown of the Wii U version, there is almost no way to guess what new features (if any) the new version will offer, though the mapping of combat abilities or dialog choices to the GamePad's touch screen (in a manner similar to how Kinect was integrated into the Xbox version) might make sense. When Mass Effect 2 was released on PlayStation 3 in early 2011, there was a digital comic that allowed the player to decide how the plot of the first game would be carried out. Since, presumably, the first and second game won't be coming to Wii U by the time the third one releases (giving Wii U owners no ability to transfer data from previous Mass Effect games over to the third, as was possible on other platforms), it would be interesting to see if BioWare takes the same approach, or one unique to the system.
Mass Effect 3 is expected to come out during the Wii U launch window, though no release date is specified on Nintendo's E3 website.