The number one reason is that Mandarin Chinese is the most widely-spoken language in the world. Learn to speak Mandarin and you can speak with millions of people around the world. More reasons:
- Business - Business people who speak Mandarin have a huge advantage in tapping into the Chinese market. It is much easier to develop all-important relationships if you can speak Mandarin.
- Travel - China and Taiwan offer exciting travel opportunities. Getting around is much easier if you can speak Mandarin.
- Culture - With thousands of years of history, Chinese culture is endlessly fascinating. Whether your interests are in history, architecture, music, or cuisine, a knowledge of Mandarin will enrich your understanding of Chinese culture.
- from About.com