For no new video content I want, no new features (they still block picture in picture on iOS app & web).
They bundle the crappy youtube music service which I also don't want.
It's a non-starter & overpriced by a factor of 5x.
There are Youtube originals but you're mainly paying for the delivery of content. Premium comes with a few extra features on mobile too.
Also you can use picture-in-picture on iphones/ipad by using the website. Play a video in fullscreen, tap to view the controls, then tap the PIP icon.