Because it is created for potency in men, and for women there are other pathogens. For example I use one viagra substitute https://kamagrajellyuk.net/ . My wife and I use it, and our sex life is intense.
Viagra is an erectile dysfunction medication for men. Viagra increases blood flow to the genitals of a man which automatically leads to erection of the penis. There is currently no licenced treatment or Viagra for sexual problems in women.
However, a herbal supplement known as PRELOX, is legally sold in UK. This supplement has shown some promise in increasing libido in women. This supplement is termed "female Viagra" among many.
Also, Flibansein, a medication originally developed as antidepressant is known to treat low sex drive in women. It works on the brain to increase sexual desire.
There is no medication proven or licenced by FDA as female Viagra.
Viagra was invented first for men in order to make sure that they have the needed bodily reactions in order to perform sex. These pills are usually purple. These were not made for women. It seems that if a woman took her husband’s or boyfriend’s Viagra, then it would not have the same affect that it does on men. In order for women to feel sexually aroused, there are other methods than medication.
Although, there are probably some medications that help arousal. There are also natural substances that a person can consume in order to be stimulated. These include oysters. They are known for making a woman or a man aroused. Most likely, in the future there may be a Viagra for women.