Now I have a close friend from China, and the mistery is solved: others are doing their exams/essays/assignments for them.
Keep in mind though, this is likely a huge generalisation (not all Chinese cheat and other nationalities cheat as well), and I put more than half of the blame on the universities themselves (they earn a lot of money accepting these kinds of students), but long-term, it really dilutes the value of this education in my eyes.