Hmmm.. motives unclear. Could be either to give you more luscious, full lips, soothe your arthritic knees, or accellerate the growth of a malignant tumor.
(Edit) Wait, are you by chance a professional long distance ski jumper?
https://gizmodo.com/the-olympics-may-have-a-penis-problem-thanks-to-ski-jumping-2000718878