The intended audience of the shuffle are people who are otherwise distracted by another task. They simply want to pick it up, hit play, and listen to music in the background while doing whatever they need to do. By moving all of those functions to one button, it creates an easier and more consistent experience.
Don’t get me wrong, I agree that having the controls available on the earbud clicker are a good idea. But they don’t need to be available only there.
Every previous Shuffle had the full control set and a Hold switch. They could have added clicker-bud support and kept the on-body controls.