cheap foreign laborers. dirt-cheap foreign laborers who will rely on emergency rooms for health care, who don't care too much whether or not their children receive a decent education, who don't think too much about retirement, and who are not very good at organizing or asserting their legal rights.
I wouldn't say that illegals don't want a good education for their kids, or imply that they're bad at all. They are pliable in the wage market, true, and the biggest motive for bringing them here is a wage suppression policy. For which wage costs can't be outsourced overseas illegals will be insourced. The Corporate Conservatives and Corporate Liberals are on the same boat with this tacit policy.
Though the border is no barrier, there are some internal ones. One of the last is the driver's license. The transport industry wants to depress the wage market power of americans and legal residents who drive for a living so they are funding the licenses for illegals drive. For the Republicans they use business front groups. For the dems they subsidize pressure groups that pose as if they represent their ethnicity.
In truth, Bush's illegal alien policy is racist, if one accounts for who is disproportionately effected - Americans at the lower income scales.