There have been many articles published on why one should learn a language, including this list. They detail languages being good for your career and interpersonal skills and understanding other people and cultures.
I have a love for languages that started in Secondary School. I have always been interested in language and how it works. Try looking at the origins of certain words, the links between languages and dialects - it's fascinating.
Languages work for different people on different levels. Some enjoy the intricacies of the language, others the ability to communicate with others of different cultures. I enjoy the challenge of speaking to people in a different language.
What I enjoy about teaching languages is that all students have a chance to excel, but especially those who are good at speaking and listening. The way of teaching is also entirely different, using games, songs and stories, as well as discussing the differences and similarities between cultures.