I've been thinking recently about the development of the Klingon language, and how it started off as a few small phrases developed by James Doohan (Scotty) and was developed into a full language over the years. Here is what I now so far, gleaned from wikipedia:
Though mentioned in the original Star Trek series episode "The Trouble With Tribbles", the Klingon language first appeared on-screen in Star Trek: The Motion Picture (1979). For Star Trek III: The Search for Spock (1984) director Leonard Nimoy and writer-producer Harve Bennett wanted the Klingons to speak a proper language instead of made-up gibberish and so commissioned Okrand to develop the phrases Doohan had come up with into a full language. Okrand enlarged the lexicon and developed grammar around the original dozen words Doohan had created. The language appeared intermittently in later films featuring the original cast - for example, in Star Trek V: The Final Frontier and in Star Trek VI: The Undiscovered Country (1991), where translation difficulties served as a plot device.
With the advent of the series Star Trek: The Next Generation (1987)— in which one of the main characters, Worf, was a Klingon— and successors, the language and various cultural aspects for the fictional species were expanded.
Why has the Klingon language been so fully developed that it could be used to produce plays and operas? I understand there was the commissioning of the language, but was that the spark? If so, why not develop other languages as well as or instead of Klingon? What makes it special, and why is it carried on today?