Currently, CarPlay can only be used by plugging an iPhone into the car via the USB port, but as part of the Apple iOS 9 update, the mirroring can be done wirelessly. No automaker currently offers a system that allows for wireless CarPlay functionality, and Volkswagen planned to show this off at CES.
So, why the block? No one really knows. Car and Driver smartly suggests that Apple is keen to control the first demonstration of wireless CarPlay, perhaps with a pre-planned partner automaker. Still, look for this technology to arrive in Volkswagens (and other cars) near you in the not-too-distant future. As soon as Apple allows it, anyway.