I agree with your point on laissez-faire capitalism. Unfettered capitalism never works. However, pardon me for beating down the straw-man. You box things in by naming a select few "socialistic" systems that seem to work (only because they've been here with everything else) and selecting a few capitalistic industries that are obvious failure. If socialism was so successful, then why don't people go to OTHER socialist nations in higher rates?

But to answer why people come here, I'd say they come for freedom and the hope of a future - and many try to stay. The east coast is full of Indian doctors who come here for their degree and have no intention of ever going back to India.