If buccal fat removal is irreversible and fat pad shrinks with age, why is it still done?

Buccal fat removal does nothing for subq fat. Most patients with chubby cheeks have both prominent fat pads and high subq %. You shrink both with weight loss, but also with aging. It's not ideal for men, as it won't allow you to get as lean as possible, you may end up overly gaunt, whereas if you have chubby cheeks, not only you will age more gracefully, but as you get ripped, your face will lean out without looking unhealthy.