Menopause or reaching middle age seems to be a factor. Some younger women do that after a series of failed relationships with men. My cousin (never met, from my estranged Uncle who cut ties with my grandparents) dated men until her 30s, then married that horse faced Berg. Virtue signaling, social pressure and social acceptance are a part of it, coupled with fact that men are less fluid than women. All women are potentially bisexual.