English rose as a global lingua franca because of two countries, first GB and then US. The rise of the English language was accompanied by the economic, political, and military expansion of these two major host countries, this trend has been continuing for nearly 200 years (I am not sure about the exact duration). Colonialism is another cause for the wide spread of the language, especially in the 19th century. So all in all we have two reasons for the worldwide use of the language: the dominance of the countries using the language (nowadays chiefly US) in the world; the other one is the sheer number of countries using English as their official (national) language, hence huge number of native/L1 speakers.  This trend would continue for another long period of time, however, when new world power arises, e.g. China, when the country's economic, political, and military influence expands, the Chinese language would also become a powerful (widely used) language. In view of the global situation, I would assume Chinese would most probably  become the next  lingua franca (but it would take decades, even centuries to accomplish this). So at least for the time being, learn English (if one is not a native speaker of the language) and try to be a global citizen.