Why?
You got me. So much for the "know what I'm talking about" bit, eh?
When you see a doctor, any specialist doctor, you see a guy who has focussed his attention of some compartment of the human body. It's like the seven wise men and the elephant. Each describes a very different beast than the other. An ob/gyn doc is not paying any attention to your brain, and we know very well that shrinks don't care about sexuality. Loss of sexuality is merely a side effect.
We are coming to realize that the brain is also a gland, in the sense of how it interacts with other glands. It is influenced by sex hormones, in a regulatory way. And it sends signals that influence the effect of sex hormones in other regions of the body.
There are so many, and so very complex, influences and interactions, I almost would say, "What doesn't affect sexuality? What doesn't influence fertility?"
Lar