From what I can see, girls always say they do while guys say that they don't. Let me try to help identify these differences.
I can tell you from my own personal perspective (as well as that from many other girls) that there are plenty of girls who like the innocent type. As far as I can remember, most of my girl friends would crush on the innocent type. So why do you never see these girls? This is usually where the guys would then give up and claim that it's because those girls don't actually exist. This may be jumping to conclusions. From personal experience and observation as well as countless of experiences I've heard from other girls, those who like the innocent kind aren't usually the type to be so vocal about their crushes. Girls who are more vocal about it tend to be more outgoing and seem to prefer those bad boys.
But then what about those times when you've seen bad boys date good girls? Once again, going off of what I know and experience, this is because those bad boys made a move on those girls. Innocent guys are also not vocal about their crushes and therefore don't typically make moves. And when they do make a move, it's usually after a girl who is vocal and that usually doesn't end too well. Innocent guys would often ignore the less vocal girls in the background who are actually interested.
And just for kicks, those who argue that science is in the favor of the bad boys should rethink. Yes it does appear more favorable for females to go after "manly men" during the hunter-gatherer days but let's face it, humans are social creatures so that type of mindset would not have lasted long anyway. The nice guy (but more generally, nice people) who always appears to finish last actually have traits that are more evolutionary beneficial. Altruistic behavior as shown in nature from birds and bats is far more favorable as it helps the community thrive as a whole. This concept works in human society too. Be nice, help others benefit, and you will benefit too.