As of January, 25% of 360 owners have a Kinect as it passed 18 million sold and also holds a Guinness world record for fastest selling consumer device.
If that's not popular then what is? Just because you don't like something doesn't make it unpopular.
I couldn't tell you the last time I've used it for gaming, but it's a pretty remarkable device for navigating the 360 and apps like Netflix.
The only thing that doesn't add up is saying that only 5% would have access to a Kinect related feature.