One simple reason: China accounts for 1/3 of the world's population. That's over 1.3 billion people that are becoming a bigger and bigger part of the world economy. No, you don't have to learn it now. But sometime in the next 20 years, it's going to be vital to your career as a nerd.
Take a look around our campus and try to argue that Chinese students don't make up a large part of the population here in San Diego. Better yet, try going to Convoy St.