Though it is not exclusive to the type of books I've been reading, most young adult sub-genre superhero novels with male protagonists have a female love interest as if mandated by society. I see the tactic as a way to interest female readers, but it never makes for a compelling narrative. That is not saying that romance isn't a satisfying genre, but shoehorning a love story into a teenage action-adventure for the sake of expanded the appeal only serves in watering down the story. However, a novel that is chock full of one gender does not have to be a turn off if the focus is spent on the story than on mass appeal.
For example, Suzanne Collins The Hunger Games trilogy is entertaining for me to read due to the plot, and I view the love triangle as a distraction. But I get it, some men do not want to read a book with all females, and the same applies for women reading books with all men. Still, there are ways to implement both genders while not smashing two together at the lips. Make interesting female characters, who have personalities and interact with each other and that should draw in female readers. Books do not always have to reflect the real world, everything doesn't have to center around love.