The OEMs are saying it's essential because that's pretty much all they offer now. Bikes must have brakes. At some point they all switched from rim brakes to disk brakes. You can hardly find bikes with rim brakes any more. The OEMs clearly believe it is a superior, essential product. Maybe they are just following the public demand....but not long ago the cycling community was strongly against them. Somehow opinion changed. Was it marketing, real-world performance, something else? I don't know, but they have become an essential component on a modern road bike.