Lol, that's actually a good question. Well, I think actual gangsters are, like, rare. It's not something you really see daily. The people you see that have the aura of gangster are trying to wear the costume they view as having either power or social currency. Ie, they want to be gangster; they want the power it implies.

This phenomenon is really common actually. In poor over-policed areas, you'll see people driving white Chevy Caprice or Impala cars because they are a reflection of the power those people view the police as having. They're basically wearing "car costumes" of the police. I don't remember the details, but this was also observed in British controlled India as well.

It is a social phenomenon for how either oppressed or disempowered groups respond to the "other."