Why Does Medicare Not Pay for (VSG) Vertical Sleeve Gastrectomy?

Morbidly Obese individuals are usually addicted to Food, have extensive health issues and are disabled (low income). Medicare will pay for mal-apsorption procedures making the morbidly obese patient looking for longevity and better quality of life, addicted to expensive Vitamins and Protein for life,or risk severe health issues. The VSG Procedure seems to limit the amount of food you can eat at each sitting without the mal-absorption problems. Why wont medicare cover this procedure?