We often promote multilingualism but really that's just for those who don't already speak English. Simply put, English is the number one language in the world and English-speaking countries are the best in the world.
If you're reading this, you clearly already speak English, and for that, kudos. English speakers often get a lot of flak for not speaking many languages but that's because they already speak the most important one.
In Europe, the UK and Ireland have the lowest levels of bilingualism, this is only because every other country in Europe learns English as a second language.
Put simply, the English speaking countries have all the coolest stuff. All the best music comes from the Anglophone world. The Beatles were from Liverpool, and with the exception of Michelle and the ridiculous German versions of their songs, are often considered the best band in the world.
Look at almost any list of the best films of all time. Most, if not all of them are in English. Sure, there are a few decent foreign films.
We'll give credit to the Greeks for some of their science all those years ago but in the modern age English is the centre of the scientific world. Even in the time of Isaac Newton, Latin was the principal language for science until they realised all the best scientists already spoke English.
Charles Darwin, though well travelled, was English. Alexander Graham Bell was Scottish and Thomas Edison was American. All English speakers and all pioneers. Even the great Nikolai Tesla, though born in what is now Croatia, was smart enough to leave and learn English. The World Wide Web was invented by Englishman Tim Berners-Lee, which is why you have "www" at the start of web pages. It's all in English.
Pretty much everything you could ever want is available in English, so why look further afield?