It's because all the people that create the programming languages speak english, and it's one of the most widely known languages in the world.
As for the Chinese vs. English thing. Yes, Chinese is spoken by more people, but English is more WIDELY spoken. Mandarin is mostly spoken in China, which is a condensed area, as opposed to English, which is the first language of most people in Canada, Australia, the British Isles, the United States, ectect.
Less problems and is better to force everyone to learn one language.
It's funny because even the creator of C++ was Dutch. ^_^
My friend was actually taught C++ by the guy in college.