Learning one language is hard enough. There are a plethora of rules and sentence structures that are hard to memorize. Sometimes you have "have had", and other times you thoroughly thought that though something made sense, it was tough to put into words. So why learn a new language if one is hard enough?
As it turns out, learning new languages can reward one with many cognitive benefits. Your memory improves, you become better at multitasking, some mental illnesses can be staved off, and overall makes you smarter. By examining your writing or thinking about what you are going to say in another language forces you to concentrate on what you are doing. If you don't you can accidentally write or speak a word that is from your native language instead of theirs.
"Multilingual people, especially children, are skilled at switching between two systems of speech, writing, and structure. According to a study from the Pennsylvania State University, this "juggling" skill makes them good multitaskers, because they can easily switch between different structures. In one study, participants used a driving simulator while doing separate, distracting tasks at the same time. The research found that people who spoke more than one language made fewer errors in their driving.
You stave off Alzheimer's and dementia
Several studies have been conducted on this topic, and the results are consistent. For monolingual adults, the mean age for the first signs of dementia is 71.4. For adults who speak two or more languages, the mean age for those first signs is 75.5. Studies considered factors such as education level, income level, gender, and physical health, but the results were consistent.
Your memory improves
Educators often liken the brain to a muscle, because it functions better with exercise. Learning a language involves memorizing rules and vocabulary, which helps strengthen that mental "muscle." This exercise improves overall memory, which means that multiple language speakers are better at remembering lists or sequences. Studies show that bilinguals are better at retaining shopping lists, names, and directions" (Merritt, Anne. "Why learn a foreign language? Benefits of bilingualism").
Along with the mental rewards, learning a new language can allow people to look inside the life of another country. For example, when I first began learning French, I had no clue about any of their culture or important places (besides the Eiffel Tower) at all. Now, I can tell you all about their important landmarks, holidays, and the overall culture (in English AND French).
It's important to learn about the world we live in instead of living inside a bubble of our own beliefs. You could even find something that resonates with you (like having a 1-2 hour lunch break) that isn't widespread in your area. It can also help to understand their native background when speaking to them since they might be apprehensive to talk about a certain subject.
Even looking at it from a logical and apathetic point of view, learning another language is useful. International business transactions can become more efficient without the use of a translator. Even in your own country, knowing another language can give your resume an edge (especially if your nation doesn't have national language). At the very least, it would help us catch up to the global multilingual rates.
"On top of that, only 10 states require some type of second language credits to graduate from high school whereas in many European countries children begin to learn a second language from 6-9 years old, or in some cases 3 years old. This stark difference in the age of when a language is taught may account for the fact that in the United States about 9% of the population is multilingual, whereas in Europe 52.7% of the population is multilingual (World Languages and Cultures)" ("Benefits of Learning a Second Language"). So with all of these rewards for learning another language, can you afford not to?