Many people in this country have no intention of living or working anywhere other than the UK, and thus no need to speak any language other than English. Without any real incentive to learn it is not really surprising that a lot of people don't care about speaking a foreign language.

Even for those people who do wish to work abroad, there is a reasonable chance that the working language, or at the very least the common language, will be English. And for those Brits who only want to go abroad on holiday, well English is learned as a second language all across the world, so some people adopt the mentality that if they do go away somewhere then they will be able to speak in English and make themselves understood.

The UK is also an island nation so we do not have a situation like parts of mainland Europe where multiple languages may be spoken within one country, or another language is spoken just across the border. It's basically a monolingual culture. Foreign language teaching is also pretty terrible in UK schools, at least in the state sector, but this is influenced by the mentality that I described above.

I think it is because there is no pressing need to speak English for Americans and British people because many other people in the world speak some English. 

If you want to know why, then it's history lessons but things like philosophers, industrial development, colonialism, wars and export of popular culture are factors.

That it is an island nation cuts itself off. Because the American economy is so large and influential, many people are familiar with English or want to learn it. So where is the incentive for a British person to learn a different language?

Echoing Romelle... I'm a U.S. citizen (learning Spanish because I'm ashamed of only knowing one language). There are many factors and, yes, some of it is simply national arrogance, but I do want to amplify what Romelle said. Please take this as an <em>explanation</em>, not a <em>justification</em>.

The area of United States (9.9 million square kilometers) is <em>roughly</em> the same as that of Europe (10.2 million square kilometers).

I don't know how to measure how much traveling "ordinary" people did or do, but my wife's mother, for example, spent almost all of her life within the state of Wisconsin and as far as I know <em>never</em> left the United States. 

I don't think languages other than English were much of a reality for her. There are various ethnic enclaves in Wisconsin where languages other than English are spoken, but to reach a place where she would have had difficulty to communicating in English, she would have had to travel 1,600 km. to Quebec, or 3,400 km. to Mexico. 

Before the age of cheap jet air travel (roughly, the 1960s)--to say nothing of cheap satellite communication--the United States seemed like almost a world in itself, an English-speaking world, with Europe, Asia, and South America feeling a long way away. When I was a kid in the 1950s "a trip to Europe" was a big deal, a luxury. In 1955 an airline flight to Europe cost USD $600 round trip, which is the equivalent of about USD $5,000 today.

This is not a popular subject. But US and UK control more than half of a 30 trillion world GDP. 

And it is true only English is necessary. I practice my Spanish on italki because it is my heritage. But my teachers tell me, if they live in foreign countries, say like Switzerland, that everyone there speaks English. They can rarely find fellow Spanish speakers.

Everywhere I have traveled, I have always found English speakers. Even in the Colombian jungle!  

What the other person said is true. The poor people in Latin American don't learn English. They can't pay the high fees for institutes of English. Colombia like Mexico is controlled by elites. Most of the ricos do speak some level of English.

Funny to hear that, being a teacher here and checking other teachers profile, it's clear that Americans and the British are the majority learning languages. When I lived in the US, I met so many of them learning foreign languages and being passionate about it. I don't know why people only mention these two nationalities when in other countries in Latin America the situation is even worse.