I know some people that think learning languages is overrated. After all, if you do not travel abroad, do not conduct business with other countries, and you are not married to someone who is a foreigner why do you need to spend months and months to learn a new language. In fact even if you are in any of the above groups you still do not need to learn other languages if you already speak English, and your partner (business or life) speaks English too. Why should we spend our time learning a new language? Why not studying something else that could be more useful for our life?
While that viewpoint is understandable, I think we need to dig a bit deeper. The value of knowledge and skills that we acquire is dependent on our subjective, and conscious experience. This is called Qualia in philosophy in which we do not understand the value of learning those things until we actually learned them. Learning math, science, art, and humanities is similar. Even travelling has the same quality. Learning other languages helps with knowing your mother language better. It brings the delicate intricate features of your own language to your attention. Knowing different languages helps with known cultures, civilizations, and way of thinking. Many people find the multilingual fluency helpful with their day to day life and with thinking clearer.
Some people complain that learning a new language is wasting time because they do not have anyone to converse with and they simply have no use for other languages. This is a bit similar with learning mathematics. Most people really don't have a practical need for math past basic arithmetic. However, learning math still opens a door of beauty and art that is only attainable to those who remains persistent. Learning both mathematics and languages is nonetheless rewarding.
People say you "understand the culture". You do not get to understand another culture unless you immerse in a native-speaking country. On a purely linguistic level you find common words and word roots (especially if you learn French or Latin which both had a significant influence on English). You will understand how the language you are learning influenced how the speakers approach the world.