First is the historical reason. This is related to the colonial history.
As we know, when the Pilgrim Fathers landed on the Massachusetts coast in 1620 after their journey from England,
they brought with them not just a set of religious beliefs, a pioneering spirit or a desire for colonization, but also their language.
Although many years later, the Americans broke away from their colonial master, the language of English remained and still does.
It was the same in Australia, too.
When Commander Phillip planted the British flag in Sydney cove on the 26th January, 1788,
it was not just a bunch of British convicts and their guardians, but also a language.
In other parts of the former British Empire, English rapidly became a unifying or dominating means of control.
For example, it became a lingua franca in India where a variety of indigenous languages made the use of any one of them as a whole country system problematic.
So the imposition of English as the one language of administration helps maintain the colonizers' control and power,
thus English traveled around many parts of the world in those days.
And long after that colonial power has faded away,
it is still widely used as a main or at least an institutional language in countries as far apart as Jamaica and Pakistan, Uganda and New Zealand.
That is the first factor.
Now the second major factor in the spread of English has been the spread of commerce throughout the world.
The spread of international commerce has taken English along with it. This is the 20th century phenomenon of globalization.
Therefore, one of the first sights many travelers see when arriving in countries as diverse as Brazil, China, for example,
is the yellow twin arch sign of MacDonald's fast food restaurant or some other famous brands outlets.
And without doubt, English is used as the language of communication in the international business community.
And the third factor related to the popular use of English is the booming international travel.
And you will find that much travel and tourism is carried on around the world in English.
Of course this is not always the case, as the multi-lingualism of many tourism workers in different countries demonstrate.
But a visit to most airports on the globe will show signs not only in the language of that country but also with English,
just as many airline announcements broadcast in English too, whatever the language of the country the airport is situated in.