If we dominate another language, it will increase our self confidence.
English is the primary language of business in the world. Most international transaction is written in English therefore if we want to negotiate with other country we will speak English.
The ability to fluently speak English as a second language can be beneficial if we are seeking job opportunities with international companies. Consequently the ability to speak a language spoken by most business people, as English, can place us ahead.
Then the majority of movies have dialog in English and subtitles in other languages can lost the meanings of words in the translation. It also entails problems in comprehension of the action. Nevertheless if we know English we can easily understand the plot.
The English language is spoken in the world, so international travelers may find that speaking English can make their travels a little easier. Most hotel and restaurant employees probably speak English. With English, we can travel anywhere in the globe and talk with native speakers.