One of the iOS 7 features highlighted by Apple at the operating system's initial unveiling in June was "iOS in the Car", a system for interacting with iOS devices not only through Siri Eyes Free but also through in-dash displays in vehicles. The feature did not launch with the rest of iOS 7, and Apple continues to list iOS in the Car as "Coming Soon".
Maybe because it's a feature that requires it be present in the car before it can be used? What use is there "launching" it on the iDevice if it can't be used? (Plus it gives them more time in testing without having to call it functional...)