In iOS 6, along with the transition into Apple Maps, had the removal of the YouTube app. It was added to the App Store as an app published by Google. It has been revealed that this was Google and YouTube's decision. It had a lot to do with the growing smartphone market and the deployment of YouTube on those devices. The decision was not affected by Apple Maps in iOS 6. Many argue that the new YouTube app is not a good user experience, which I can vouch for. While the old YouTube app designed by Apple would not work today, we would see support for picture-in-picture since it would be designed by Apple. The fundamentals of the app would not be changed as frequently as it is today. One example is how a recent minor update completely changed how the scrubber bar detects when it is being pressed. And of course, there would be less bugs and glitches. YouTube uses a custom-made "Material" design used in Android. However, that doesn't work in iOS. Icons are different, it looks foreign, and it leads to bugs. Orientation may get stuck and buttons may not work. Anyways, rant over and mystery solved.
...2012 iOS6, time for YouTube to take back control of our app, which was still Apple-created. Made gutsy move to not renew agreement...— ✈️ to the ⛰ (@hunterwalk) June 30, 2017