It is the most useful international language in use in the world today. Those who bemoan in frustration why don't they just learn English? are labelled as culturally insensitive by the left, who feel that English speaking people have an equal obligation to learn someone else's language. The question is - which one?
While French or German may have seemed good candidates for an international language a century or two ago, the French lost the battle through their own isolationism, and the Germans were just too unpopular. English is spoken by more people in more countries than any other language and is the rational choice for those who want to communicate globally.
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