Lots of people, it seems! Tauty, from Belgium poses this question (on a card designed to help a person learn (and love) English):
Why has English become the language of Post Crossing?
According to listverse.com, English is NOT the language spoken by the most PEOPLE in the world. English is number 2 in that contest; Mandarin is number 1. However, English is spoken in the highest number of countries.