Supply and demand, free markets, capitalism, etc...
But don't you think that the more sinister aspect of this laissez-faire 'capitalism' you espouse is an active interest in keeping a certain percentage of the population uneducated and desperate? Right now, Mexico has no interest in providing for its own population, because they can be farmed out to the U.S. In return, the U.S. has no interest in putting pressure on Mexico to reform, because Mexico is a source for an endless supply of cheap labor.
(If I don't respond tonight...I've got to get some sleep, but I'll try to get back here tomorrow).
Why don't you just move to Mexico? Sounds like they've already got the exact culture you have in mind. An unlimited supply of coolie laborers --- so much they're desperate to rid themselves of many of them. Why be in the USA where you might have to pay these chumps $3 an hour when you could live in Mexico and pay them $0.30 an hour? And they've got the racial stratification you adore already firmly in place.