Necessary it's not. Some people are perfectly happy with their jobs, living in the same country for the rest of their lives.
I do believe it will enrich your life if you try life and work out in another country. It will teach you all about another culture, new traditions, different people and strange rituals.
This way of life makes me a happier person, knowing I learn from it and find out how flexible I really am. Advisable it always is! Necessary it's not:-)