Maybe if they worked so hard, things would look a whole lot different where they used to live. You have to ask yourself why the same people who created such a crappy system or allowed it to go on (remember --- Mexico is a democracy) are going to be different just because they moved en masse 1000 miles north. They keep their language, their culture, their politics ---- things will end up the same where ever they go.
Take a look around Southern California, much of it looks like a third-world slum....yet nothing is ever done about it. Both parties are equally at fault for this mess.