On the Viagra - Birth Control Analogy

I've never understood it. Viagra is for a medical condition and birth control is something that you take to avoid pregnancy (which is only a medical condition ONCE IT OCCURS). A much better analogy would have been to compare Viagra to something that makes it easier for a woman to have an orgasm or even to a fertility drug....Now, if the birth control in question is something that a woman needs to treat a medical condition, that in fact WOULD make it an appropriate analogy and something that the insurance should cover.