You don't know the extent of human bias. All humans are ruled more by bias than by logic, doctors included AND you included as well. What's especially worse is that Doctors are trained to mistrust a patient. They view patients as lower ranking simpletons so they trust established knowledge more than they trust a patients description of an anomaly. The key here that you have to realize is that what the doctors are doi…
Perhaps having a certain percentage of gay or asexual people helps the entire group survive better. Maybe it is an archaic form of division of labor? Some individuals will specialize on breeding, others on guard duties, hunting etc.