Because it links up an incredibly long and incredibly hostile bit of territory, and essentially hooks the rail networks of Asia with the ones in Europe. As a r

Because it links up an incredibly long and incredibly hostile bit of territory, and essentially hooks the rail networks of Asia with the ones in Europe. As a result, I can walk to my local train station here in the North of England, and ride a continuous set of trains all the way to Ho Chi Minh City (Saigon) without ever stepping off the platform. If it weren't for a few destroyed tracks in Cambodia, you could make it to Singapore. That's pretty cool. It's also the cheapest per-mile transport on earth. Where else can you get a full third of the way around the globe for under $200?