Sexual desire is not valued because it is not necessary for a woman to have desire in order to participate in partnered sexual activity. And if sex can occur without desire, the thought that follows is that lack of desire must not be a serious problem.
Most women think it's natural for their sex lives to wane over time, and going from having sex several times a week to just a couple of times a month (if you're feeling lucky) is no big deal. The reality is: It is a big deal.
Desire ebbs and flows, both throughout an individual's life and throughout the context of an individual relationship. So, I think it is useful to come up with strategies to minimize the impact this may have.