Because they can't work or can't work for as much in their country.
many do so for the chance to LEARN about other countries and other cultures than their own.
It is because of the fact that the respected country is not performing well economically so they choose to shift in that region where the economy is better so they can earn better.
For a better living.
Americans seldom do.
I think the reason behind work in abroad is remuneration.When negotiating the terms of an overseas assignment, it’s possible that your employer is going to reward you for the risk you are taking by going to a new country. Often you will only be offered an overseas opportunity because the business feels that you have the ability to deliver for them where someone else cannot.