May be due to cost effective to produce in Industrial scale, so industry shown interest only on synthetic contraceptive production. even in research also priority given for in lab scale not in industry
There is continuous extensive research in hormonal contraception, mostly I think industry sponsored/ organised. Millions and millions have been spent.The golden grail is finding patentable hormones for the pill which do not increase thrombosis risk but give even better cycle control, even less acne, even less hirsutism perhaps less even less pregnancies, perhaps decrease or increase in libido as required. Less mood change or more mood changes as desired. Pills which could be combined with heavy smoking or high blood pressure. This research has not been very successful (yet). The pharmaceutical industry is more or less desperate because patents have long run out and there is no pill really better than second generation pills. They use therefore a large part of their budget for framing and marketing to convince us that past second generation pills are better, in many countries they are very effective