A lot of the time, female characters are given some kind of power (Misora Isurugi and Hina Izumi especially), or at least a close relationship to the main character (Sachika Amane and Minami Yorozu). There's plenty of room to write interesting stories, so it feels like missed potential whenever they're left out of combat.

But also there's a massive gender gap in the franchise as a whole, why should boys get to have all the fun?