Why do our poor stay poor?

I want to study this topic more intensively, but to start it off, check out the WSJ and their article on "payday" loan centers. It's just another case of lenders taking advantage of those with low (but stable and guaranteed) incomes by offering them financial freedom when indeed any freedom they might have had goes out the window as soon as they sign the contract.
These lenders are giving out small loans between $200-800 which then must be paid back with these people's limited income. I don't know why these folks think it's a good idea to take out a loan to pay for necessities that is in some cases around 75% of their monthly income. There is NO WAY you are paying that back with a constant but tiny income when interest (up to 300% in many cases) and fees are applied to the initial amount every month. These lenders take advantage of the fact that the government is supplying this steady stream and the fact that they can take control of the person's SS checks, take out their cut, and pass the pennies on to the individual. The cycle of debt for the poor continues.
These lenders are similar to the"rent to own" retailers that allow low income folks to purchase higher cost consumer goods at huge interest paid over an extended period of time. We know that the poor have an unhealthy obsession with material goods, so mustn't we exploit it for our own profit, widening the gap between the rich and the poor?