What do you mean by "so many"? We usually write for our own gender, and the male authors show a slight edge in numbers. I see many fiction books about war, politics, law and order, and while women are active in these areas (and would be inclined to read about them), the books are usually written by men and use words more likely spoken by men. The style is masculine. Horror stories and thrillers are primarily geared toward men.
I presume more women read romantic fiction (How else would Harlequin Enterprises put out at least two dozen of their own in various categories every month?) and we are fond of cookbooks because we do most of the cooking - though there are many professional chefs and bakers who are male. I'm fond of social history, which is usually written by women; but most political history is written by men. Sports: mostly written by men for a male audience; though women authors are growing in numbers. Crime and politics; mostly male authors. Childrens: mostly female authors.