You don't need to be beautiful/handsome to be sexy. These are two very different things. Likewise not all (not even most) beautiful people are sexy. For instance, a very beautiful woman that is too cold and serious, doesn't care about clothing and doesn't wear make-up may not be sexy. Sexisness is more about one's will to arouse other people. It's in the mind and in the style, not really in the physical beauty.