Like others mentioned, I find that the areas that have higher disposable incomes are a lot more wasteful with re-saleable items. The "poor" neighborhoods are better for shred weight, I imagine they aren't able to pay people to haul away their junk and they are not knowledgeable of the scrapyards in their areas.

Of course, laziness can affect a person of any financial status, so they'll just throw everything away, rather than deal with fixing, selling, or sharing with others.