Why are girls so uncommunicative?

So, I am talking with a girl currently. We both talk about many things and text intimately. Most of the time i initiate the text, i say so many sexy things and she reacts nicely & loves it but she never expresses herself. Even if I ask she hesitates but she is comfortable with me saying anything to her. I can't go on forever. I want her to talk to me in that way too. why are you girls like this. why don't you communicate openly and how can we boys make you talk? Please girls, help me.