Also, the pill for women was the first product and therefore only had to be better than the alternative. A pill for men would be a substitute to the current one

Also, the pill for women was the first product and therefore only had to be better than the alternative. A pill for men would be a substitute to the current one for women and would therefore have to show improvement over that. Investing several billion $ just to end up with a drug that has the same side effect taken by the other gender is not a wise investment. Yes, there's the topic of gender equality, but there are already other alternatives that come with less side effects (but are less convenient).