As Kipling said, "What do they know of England, who only England know?”
What that means is that if you lived most of your life in your home country and have not gone outside, you wont gain the perspective to REALLY know about your home country. It's only when you go outside do you really gain perspective about it.
In my case, there are so many things I learned about the UK only since I travelled to many other countries. About the people and their motivations, their behaviors, the culture, the perception, the life, the infrastructure, the government, the economics, where your country fits in the world and how it is placed in the world and so on.
Apart from all that, the experience and knowledge you gain by seeing the rest of the world and learning about it totally changes the way you think and you definitely will understand the world MUCH BETTER than you did before. You will meet people you never ever would have met before.
Another plus is that if you ever return to your home country and join the work force, the travelling you did adds huge value to your Resume because it makes you totally stand out and, if you're in business, somehow there is a large and significant chance it can also make you wealthier because you may have discovered some good arbitrage opportunities along the way.
What Anton Kreil said about this is basically to the point.
