They're people, they can't be all that different.. they choose names they like for some reason
That's a hugely good point! There is obviously something about these names that is attractive to those who use them, whether we can see it or not.
One thing that isn't "PC" which I have noticed, is that often, people in low income/welfare, poor education, downtrodden minority etc situations feel as much contempt for the well-heeled middle class as the middle class does for them (I've been on the receiving end of it from my stepmother, who has two kids by two different fathers and could barely read before she married my Dad). The names which shock and horrify the middle class may well be intended to do so - the names set up a distinct barrier of "We are Different to You", which upsets a middle class convinced that the goal of the welfare class is to attain middle classness (ie assimilate with their cultural norms).
I'm just theorising here, so I could be totally wrong! And of course if I'm right that's still just one element of a complex naming pattern. But I understand your feeling of a "culture secret".
Re the Aboriginal statistics: yes, it's the same everywhere. What I always find bizarre, being "outside looking in" on US society, is the lack of reference to Native Americans. I'd guess you'd have to watch a hundred random modern American films to see one Native American face, and even then he/she would be in a stereotyped role. Where are the ordinary Native Americans going about their daily lives in the suburbs?