Here are some reasons why speaking English is a really great idea:

Language of diplomacy:
English is the language of diplomacy, with many international organizations using English as their official language.

Language of aviation:
English is the language of aviation, with pilots and air traffic controllers around the world using English to communicate.

Language of science:
English is the language of science, with many scientific discoveries and breakthroughs being published in English.

Language of technology:
English is the language of technology, with many software programs and applications using English as their primary language.

Language of entertainment:
English is the language of entertainment, with many popular movies, TV shows, and music being produced in English.