The Concept of Different Languages

I know, that's an odd title. Let me explain: The concept of different languages for different regions and people isn't new to us; we experience it every day in our own world. Some think it's cool, others are simply annoyed because it makes communication more difficult. However, there has to be something logical and "right" about it as it is used in many created worlds as well.

The example of RPGs comes to my mind because I played "Pathfinder" yesterday. Guess what, I played a librarian with high ranks in the linguistic skill. My character spoke 10 different languages! Literally every group of beings intelligent enough to speak at all had their own language, like Dwarven, Elven, Draconic, ...

But, it's not only RPGs. Only think about Tolkien and his elven language. He created a whole language, with comprehensive vocabulary and grammar, for his books! Many other fantasy books and films at least embrace the concept of various languages, without actually introducing a language of their own.

My conclusion: The concept of various languages seems to fascinate a whole bunch of people. It just makes sense that people who live apart from each other, have different cultures and are of a different race should have different languages as well. And ususally, in those games and stories, it's the one who wants something from the other people (passing through their territory, trade, information, you name it) who has to learn the other language. People in those games and stories do not expect to be greeted in their native language when they travel elsewhere. So how comes that in real life, there are so many people who travel without the slightest knowledge in the other language(s)? Who expect people around the world to speak their native language? I say, read and watch more fantasy, and then, when you have finally grasped the concept of different languages, get your butt up and learn at least some phrases and words before travelling elsewhere or asking foreign people for something...