One reason why we pity geeks is because we think they are missing out on life, focusing their lives on things that ultimately don't count for much. (And the single bachelor geek who can't relate to women is missing out on something which can be described, without too much exaggeration, as having cosmic importance!)
One example to which I alluded in a post yesterday is spending one's time to learn a completely made-up language. (Whether we should include Esperanto as falling under this discussion I leave to the reader to decide.) How many people have used their leisure to pick up an Elven language, Abh, or Klingon [wiki, Yamada]? There are undoubtedly many who have learned Klingon for the sake of using it at Star Trek Conventions. (When they dress up for conventions and such, why do people pick the alien characters they do? Does it reflect anything in their personality?) As far as I know, no other Star Trek language has the same amount of development of Klingong--there are fewer speakers of Vulcan or Romulan, for example.
This is definitely not like the study of Attic Greek, Latin, classical Chinese, or some other "dead" language that is still used in certain situations (e.g. as a liturgical language) or "lives" in written texts and a tradition. Even if one did not need Latin to become involved in a tradition, knowledge of the langauge would help one's familiarity with English vocabulary and thus have some practical value. Hence, there is more utility in learning languages such as the ones I have mentioned, and is a better use of time. And how we use our time is of importance in the light of eternity... If our leisure is not being used well, in accordance with our vocation and state of life, then we should be criticized and humbly accept it...
Could not the same charge be levelled at the creators of such languages, such as J.R. Tolkien?
Here we must distinguish between those who have a vocation to be an artist and those who do not. An artist such as Tolkien has a vocation to create (of course in accordance with good art but also to reflect a "moral universe") , and I would not consider this a waste of time. It is the imagination put to good use, so long as the artist is fulfilling what God is calling him to do, for whatever purpose God has charged him with. Such attention to the minutiae of story-telling is usually helpful, but of course needs to be subordinate to the greater aims of the work. If fine details were present without a story (or with a bad story), then we would have to judge the work as a whole a failure, even if it is in accordance with the artist's designs. That is to say, while it may be true as a product of the artist's intellect, it may be mostly false as a depiction or reflection of reality. Those forms of art, such as fictional literature, that do represent reality, even if not in a straightforward manner (as in other genres, or like a philosophical text), must be judged according to this notion of truth, and not solely according to productive or artistic truth.
Still, one can understand the escapist mentality of those who become devotees of Tolkien, fantasy, science-fiction, anime, manga, comic books, video games, movies, television dramas, even music (as when the attachment to music becomes disordered in some way). (And believe me when I say I include myself in this category of people.) There is much in our contemporary world to cause sadness and the desire to flee, and much that is lacking that should be present for a humane existence. It's just that there are better ways to flee, even if one must remain in the world to engage with it.
More on Esperanto: