appearances

I have often wondered about people and society while sitting in court.
The way people dress creates a stereotype...or does the stereotype dictate the way someone dresses? For example, what makes someone who is trailer-trashy dress in tights and a ripped mini-skirt with hooker boots, an over-the-top low-cut shirt that shows way too much cleavage to be appropriate and messy bleached and teased hair? Is it because something in their history told them that was a "sexy" look? I can only assume most of these people have access to a television, and if not, they must leave the house and see other people dressed well, or at the very least, appropriately and tastefully. So, why the trailer-trash outfit? What made them think it was a "good look"?
I have also wondered, looking at people who have obviously had a hard go with life, whether those people look as rough as they do because of their lives, or because of a stigma? For example, when a person is known as a cocaine addict, do they look as rough as they do because they really are, or is it because I know they have drug problems and likely live a dilapidated lifestyle? Would they still look as harsh if they were clean cut and dressed in a suit, for example? The facial features would still be the same.
Which came first, the assumption someone lives a broken life, or the appearance they do?