The skin is a fuctional organ, even if people don't think of it as such, and "necessity" for something that improves quality of life is recognized. Just like psychology is recognized.
The article broaches this argument over "necessary";
The challenge gets even more daunting in court, where questions of medical necessity often boil down to a matter of opinion, with dueling assessments from each side's experts.
The article seems to be defining "necessary" as a procedure where the benefits outweigh the risks, and "unnecessary" as a procedure where the risks outweigh the benefits. Then goes further and shows statistically how to detect surgeons diagnosing and treating conditions based on profit rather than patient benefit.
The research is by the Journal of the American Medical Association, the Journal Surgical Neurology International, and Dartmouth College's Institute for Health Policy and Clinical Practice, which seem like reliable sources.