title_body: Why learn constructed languages? I understand why create conlangs - they are sometimes needed for world of a book or game.
  
  But... why learn them?
  
  If most people in the world know normal languages and speak them, we can communicate with them using existing languages. There is no problem with talking with someone without knowing his language, because nowadays a lot of people in the world speak English, which is kind of an international language.
  
  I couldn't find a real reason why. We don't talk with characters inside books or movies. We do eventually talk with in-game characters, but they rather speak a normal language, not a conlang. If they don't do so, then we can still understand what they want to say, because games often add some kind of translation, if creators of the game want the player to understand the message.
  
  Is learning constructed languages ever necessary? What are the possible reasons of learning a conlang?
  
  EDIT: I don't think this is opinion based. I'm not asking "why do you learn conlangs?" I'm asking for the most common reasons why people learn conlangs, not for opinion.
upvoted_answer: An unordered set of potential reasons:
  
  
  Showing off. I know something cool that you don’t. For some, that is the reason to learn Latin but for others that may be the reason to attempt to learn e.g. a language from the Lord of the Rings. It can easily have a vast impression on fans of the franchise.
  Cosplay. This is especially true for languages appearing in games/movies/etc. For many cosplayers, the prime goal when cosplaying a character is to mimic them as perfectly as possible. Of course, if you’re mimicking e.g. Eragon after he has learnt the ancient language, you want to at least be able to produce meaningful sentences (unless you’re explicitly aiming for mishaps like the one in the underground city — but arguably that requires even more knowledge). If you’re cosplaying Arya, that is even more true.
  Creating a franchise that uses a conlang. If you want to make extensive use of your conlang while writing a series of books like A Song of Ice and Fire, getting it right at later stages is much easier if you have some basic understanding early.
  Just because they can. For some people, picking up a language is extremely easy so they may just want to do it for intellectual stimulation.