It's a result of the British empire, and later America's cultural influence on the world.

Hello Student 1413: It is because people all over the world want to learn it. There is no official policy or advocacy to make it such. It just seems that so many people seem willing to learn it, for business, for travel, as a means of expression in literature and education. ---Warm Regards, Bruce

This is because the British Empire is the largest empire in the world not in terms of land mass but how far flung it was. Except for Arctica and Antarctica, the British somehow has a colony there. So the language is widespread. Remember even the US was a former colony.

The use of the term "lingua franca" described in this article arose from the name of a particular example of this type of language. Lingua Franca was a mixed language composed mostly (80%) of Italian with a broad vocabulary drawn from Old French, Turkish, Greek, Arabic, Portuguese and Spanish. It was in use throughout the eastern Mediterranean as the language of commerce and diplomacy in and around the Renaissance era. At that time, Italian speakers dominated seaborne commerce in the port cities of the Ottoman empire. Franca was the Italian word for Frankish. Its usage in the term lingua franca originated from its meaning in Arabic and Greek, dating from before the Crusades and during the Middle Ages, whereby all Western Europeans were called "Franks" or Faranji in Arabic and Phrankoi in Greek during the late Byzantine Period. The term lingua franca is first recorded in English in 1678. The use of lingua francas may be almost as old as language itself. Certainly they have existed since antiquity. Latin and Greek were the lingua francas of the Roman empire; Akkadian, and then Aramaic, remained the common languages of a large part of Western Asia through several earlier empires.Examples of lingua francas remain numerous, and exist on every continent. The most obvious example today is English. There are many other lingua francas centralized on particular regions, such as Arabic, Chinese, French, Portuguese, Russian and Spanish.