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.