Mass Effect 3 uses the Kinect for voice recognition instead of the headset because it’s built into the hardware and Xbox software. If Bioware was going to develop their own voice recognition from the ground up they would have left the feature out. Also, if Bioware had to purchase the technology from a third party company it would have been too costly. It wasn’t an evil plot by Microsoft to sell hardware where money bags exchanging hands, it was one employee trying a proof of concept that turned out to be a cool feature.