Why do women hate nice guys?

Back in High School I used to be the nicest guy in the world because that's what I thought women wanted. I learned how to play guitar, would write songs for girls all that typical cliche' nice guy stuff. Then I realized wow, I am 20 years old and never had a girlfriend or had sex before I should probably do something different. Well I changed my attitude completely and started to not care about anything when it came to what women thought of me. I used to take it is so personally if a woman didn't want to go out with me, now I could care less. When I talk to women now I always act like I can do better and it works. I have hooked up with more women in the past 2-3 years than I ever had in the 1st twenty. One thing is tho, I don't act like an @sshole and degrade women, I am still nice, I just revamped my personality and kept a certain mysteriousness about me and took it too a new level. So why do women hate nice guys and seem more attracted to guys with a little bit of attitude? Don't get me wrong I am still a nice guy, I just carry myself different and it works.