Buy two get one free

I caste my eye over a tabloid today, and there was an advert smacking me squrely in the face. It was for thermal gloves. They were made from a material which generates heat while being worn and so helps joint movement. But it wasn't so much their function which interested me, it was the red star which said "buy two and get one free." Well normally two gloves would be useful, especially for those beings with two hands, however how many people have three hands? Who would be using the third glove? No one I know.