I can't say how deeply sad it makes me that we have this perception about creating languages -- that it's something you do if you want to have silly wacky fun in your fantasy book or movie.

I agree, but not for the same reasons. Artificial auxiliary languages just Don't Work. You just can't reasonably expect to do any better at that than Esperanto did, and Esperanto can hardly be seen as "successful" as far as its original goals are concerned. It has essentially simply developed into yet another language of a specific cultural-linguistic group- made up of people from lots of different source cultures and languages, but a distinct cultural entity nonetheless.

No, the real tragedy of the public perception of artificial languages as nothing more than props for books and movies is that it blinds them to the fact that language creation can be fulfilling in many other ways. People create languages as experiments in psychology or logic, as a hands-on learning experience to better understand linguistics, or (and this is what I lean towards most strongly) as independent artistic creations that have aesthetic value in their own right.