Because for some jobs you don't need qualifications. If you think that a university professor from eastern Europe is going to come to Germany to clean toilets, you're really in for a surprise. For cleaning toilets, you'll get a guy who doesn't have any qualifications. From my short experience in the US, I got the impression that no one had any problem with immigrants as long as they took jobs Americans didn't want. But, when they started taking jobs Americans actually do want, there's an immigration problem.
But, you guys are all forgetting that you need increasing population to keep the economy going. I remember reading that in the next several decades, EU is going to be short of about 20 million workers. So, like it or not, EU will have to import workers or the economy will suffer. I don't have the numbers for US, but I'm sure it's a similar situation...
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