Because the "bad girl" attitude is very in at the moment, in case you hadn't noticed. Artists like Pink, Lady GaGa, and even as far back as when Britney Spears came out of the woodwork to try and revitalise her career. Girls aspire to be that "bad girl" and guys all think it's hot. Perhaps "bad girl" is the wrong term, but a free spirit, a renegade, loud and proud, you know what i mean. A typical "i'm totally defying gender definitions by not only flaunting it, but by ridiculing it". It's the type of "i want what i want but you're not necessarily the one to give it to me" attitude that Bayonetta exudes. Sexually aggressive is perhaps the term i'm looking for.