There are very many reasons why people emigrate from their home countries.

If we disregard political aspects of persecution by some regimes the 3 most often quoted reasons are: economic, social and environmental arguments. Many people emigrate in order to find a job or better payment. They want to avoid excessive taxation which is usually the case of celebrities. The poor or those made redundant secure basic needs. The celebrities like Sophia Loren try to be even richer. All of them look forward to better life opportunities of their children. Some people leave their countries to improve their social conditions. They r often in need of better health service, educational opportunities or developed shop chains. For some people the social factors r often more important then money, political ideas or other ambitions.Those who appreciate clean environment and the beauty of nature may emigrate because they want to find less polluted area where the wild life prevails. They may also prefer better climate or seasonal weather. For example some skiers may like living in the Alps or the Rocky Mountains.
As one can see people may leave their homeland in search of new, better life for many reasons. The mentioned above may be quite popular but particular cases the reasons might be very unique and individual.