Insurers cover drugs that aid return to homeostasis (the normal functioning of the body), not drugs that interrupt the normal functioning of the body. That is why viagara is a covered item. If there were an equal drug that aided women with sexual dysfunction, it would be covered.
http://www.psy.utexas.edu/psy/ARTICLES/news_meston.html
EXCERPT: "Some call the drug the female equivalent of Viagra, but unlike its male counterpart, it is not likely to be covered by insurance companies, Meston said. Insurance companies pay for Viagra because arousal is necessary for men to reproduce," Meston said. "But, there is no evidence linking female sexual satisfaction with their ability to reproduce. Unfortunately, this will keep most insurance companies from covering this type of drug in their policies."
Huh? Not wanting sex would seem to me a hinderance for women to reproduce, unless they are advocating rape.