There is usually a subplot involved, about the shameless way that advertisers use sex to market to teens. It's true that marketers are probably shameless, and that most people want their stuff to make them sexier, but the ideology behind the perennial screed about materialistic teenagers is that it implies that there is some ideal world that we all live in, a world in which the content of our characters does not have to be communicated by a corporate logo emblazoned on our ass. But it doesn't work that way, not as long as we have castes in our culture. How we consume says everything about who we are. This is why those who hate logo tees, Louis Vuitton and Tommy jackets hate them with such a passion.
Inconspicuous consumption is much more expensive and much more difficult to master.
I know, because I managed to lose my class identity and had to negotiate ways to get it back. One way was by buying stuff, certain stuff, to rehabilitate my outward appearance. I did this by becoming a parent at a scandalously young age, one of the most efficient routes to poverty. My plunge was particularly weird, because when I fell out of the middle class, I landed in the upper-middle class, arriving with a heavily subsidized education at a very expensive, very liberal, very private East Coast university. I don't know what constitutes class identity for a teenage single mother from Idaho who is quite literally the only one of her kind at a private school.