Yes the answer to your question is CULTURE! For example- I am in Japan right now, which was closed off to the world for hundreds of years, as well as being geographically isolated - what comes of this is a unique and highly artistic culture and mode of life. When people move from one country to another they bring THEIR culture with them, and while their culture might be awesome and great , it displaces always the culture that they are moving into - thereby diluting it. Yes and of course countries also want to protect their economies as well. I have had the opportunity to visit Thailand and Japan many times over the past two years - what is the difference between these countries? I love Thailand, and its people and culture, but Bangkok looks like its just been through a 50 year war, there are literal holes in the sidewalk that you could fall into the open sewer, while I have yet to see a single pothole in Japan.. In Thailand people hardly pay attention to traffic signals, and the streets are very dangerous, one of the highest death rate on the highway - in Japan I have NEVER seen someone disobey a traffic signal. In Thailand there are piles of trash everywhere, again very hard to find in Japan. In Thailand its common to walk into a shop and see the three or five employees sitting on the floor eating food and talking - when you ask for help to buy something they slowly get up and shuffle over to maybe help you a little...in Japan there would be one employee who would be the most helpful, friendly, and efficient person you have ever met. So what is the difference? Has Thailand been under some colonial rule or horrible war? No - actually the opposite. The difference is CULTURE. So what would happen if you took half the Thai people and put them in Japan and vice versa. Loss of culture - loss of a peoples soul that took thousands of years to develop. Nothing against Thailand BTW - the people are happy in Thailand and I wouldn't want to see a loos of their culture either. Just food for thought.