First, let me quickly go through the reasons that people commonly list for learning a new language.

1. You gain a new perspective.

Each language you speak alters the way you view and interact with the world, especially if they are from regions that are culturally very different. For example, I know for a fact that I become more respectful and cautious when speaking to older Korean adults. Obviously, the custom in each region plays a huge role, but the language itself does as well. For example, I saw a Korean TV program that showed footage of married couples getting into arguments while one was teaching the other how to drive. A therapist recommended using the formal tone (in Korean, using the formal tone changes not only the vocabulary, but even the grammar) while conversing in the car. The couples became much more considerate and stopped snapping at each other over time. It’s not difficult to understand how language can evoke completely different emotions. Think of freedom fighter vs terrorist, advance vs invade, chat up vs holler, etc.

2. You become more employable.

I lived in Spain while the youth unemployment rate (those between age 15-24, myself included) was 45-55%, although some claim that the statistics are exaggerated:

“Any increase in the proportion of young people who decide to delay entering the labour market and keep studying – and remain economically inactive – has the effect of increasing unemployment figures because the number by which the unemployed population gets divided by shrinks. But importantly, the overall number of young people stays the same.” –http://www.bbc.co.uk/news/business-19745115

The situation is still pretty bad considering the emigration of thousands of Spaniards in search of jobs and the prevalence of the mileuristas, those who make about 1000 euros (1300 US dollars) a month. Despite all of this, I received more than twenty job + interview offers in teaching, sales, marketing, business analysis, project management, etc (my resume was stored in a job search website). I graduated from college two years ago, so I know that my language skills was a huge factor.

3. You become more conscious or knowledgeable of your own language.

My dad once told me that his theory for saying “you are” instead of “is” like how the “be” verb is conjugated in all the other singular pronouns is that “you” implies that there is more than one person involved in the conversation, ie, the speaker and the audience. You rarely see monolingual people make observations like that.
Now let’s get to the less obvious reasons.

4. Speaking more than one language has remarkable effects on the brain, such as heightened sense of awareness and resistance to dementia.

As reported by the New York Times in March this year, and then by the Wall Street Journal a month later.

5. For me, the biggest reason is that I can be productive while slacking off or socializing.

For example, I was constantly learning and practicing Spanish while going out for beer with my Spanish friends, and brushing up on my Korean every time I talked to my family and friends after an extended time of not speaking the language. When I feel like being lazy, I can be productive by just listening to Spanish music or watching Spanish TV. I can even be productive while I shower. I couldn’t roll my “r”s in Spanish, so I would practice pronouncing “arr” “err” “irr” “orr” and “urr.” Now I got it, although sometimes it still takes effort. Now I practice pronouncing the French “r” while in the shower.

Finally, I would just like to add that each language I speak has enriched my life tremendously. All the friends I made, books I was able to read in their original versions, and the life experiences I had that was possible due to the languages I know are simply priceless. I encourage everyone to learn at least one foreign language.