It was at the beginning of 2004 when I read Watchmen for the first time. It was not from a magazine. I read it from a low-quality set of scans that I found in the corner of the pre-torrent Internet, on a gigantic 21" CRT monitor that I used at work. My productivity fell for the two days it took me to read them without being too obvious, and I became an instant fan. In the end, I said to myself: "Somebody should make a movie out of this."
Watchmen was adapted five years later, and the apocalyptic warnings of Alan More himself were ignored for the sake of curiosity. Yes, it was a decent visual spectacle. Still, it never went beyond a (not even faithful) shallow plot and never convinced us that Patrick Wilson was out of shape and in a middle-age crisis.

So, where does this overwhelming desire to adapt any creative work into a film come from? Knowing that in most cases, the best any of us can expect is to say "well, that didn’t ruin all the love that I had for the original."
It is obvious why film adaptations are made. Nowadays, every IP has to be a franchise. Value has to grow eternally, and no market can be left unexplored. Nothing can just "be." And it is understandable. Not everybody has the iron will of Bill Watterson to reject hundreds of millions of dollars to save Calvin and Hobbes from commercialization. It makes perfect sense when expressed in dollars and cents. But why we, as an audience, crave those things? Is it because we are now part of the cycle, and we expect it?
Marshall McLuhan said: "The medium is the message," and argued that the character of the medium, not the content, defines the delivery. The nature of cinema, and the way we understand its language is what makes films great. Content is just an excuse to use the great tools that cinema provides. I think that it would be safe to assume that even the same content will be different in different mediums because they are delivering different messages.
When I read The Dark Tower (as someone with English as a second language), it took me some time to understand the joke behind "When is a door not a door? When it is ajar." You cannot translate this joke, because the language (as a medium) is what makes the message possible. This content cannot be adapted without being destroyed.
This is not a revolutionary point of view. Nobody will argue a live feed of a football match is a suitable replacement for watching it live. But we are so enamoured with the idea of cinema being the ultimate medium that we think that it can handle any "mistranslation." Cinema attacks a lot of our senses. It can release a wide array of information per frame, and the only thing it asks from us is ninety minutes of our attention.
Is this why we are so obsessed with the idea of adaptations? Are films the cultural equivalent of the info dump that makes Neo react with "I know Kung-fu"?… do we really know Kung-fu?
Let's go with the obvious: Book adaptations.
It seems like a match made in heaven, mostly because reading books is hard and takes time. But the language of the literature medium and of the film is, obviously, really different. We expect a movie to close a plot in two hours or less, while a significant majority of books do not even care about the idea of a plot or resolution. Streams of consciousness, internal monologues, character examinations, studies of the surroundings; while they are common in literature, don't make exciting films. A film director might interiorize the words of an author about a sunset at the rocky mountains and deliver a breathtaking shot. Still, the brain cannot absorb all that information the same way it does when the author slowly lets us know, word by word, for a whole page how the sun hides behind the rocky faces of The Three Sisters. Both approaches for the sunset, even if they are excellent in their own right, end up being two different products with different purposes.
The book-to-film adaptations have two main jobs. First, to bring into reality the faces, voices and places that (assuming you already read the book) your brain had to imagine. Second, to quickly summarize the plot (if there is anything of that.) If the director is good, she will create a newly translated joke, maybe not about doors not being doors, but about socks also being glasses. In conclusion, most of the things that make a book great, have to be cut out to make sense on a big screen.
The book-to-film adaptations have two main jobs. First, to bring into reality the faces, voices and places that (assuming you already read the book) your brain had to imagine. Second, to quickly summarize the plot (if there is anything of that.) If the director is good, she will create a newly translated joke, maybe not about doors not being doors, but about socks also being glasses. In conclusion, most of the things that make a book great, have to be cut out to make sense on a big screen.
Film directors, being the professionals they are, understand this basic idea pretty well. When there is no need to sell toys, there are other alternatives to adapt the works of different mediums. The "loose" adaptation, the "what if" version, the "pick it up and run away with it" work. One of the best examples of this is Apocalypse Now!. It was based on the novella Heart of Darkness, written by Joseph Conrad eighty years before the release of the movie. The film uses characters with the same names in similar situations under analog environments (the Belgium-controlled Congo vs American-intervened Cambodia), and it tells a story that, by necessity, needs to adapt to the new circumstances established by the writers. Even when it copies several bits at verbatim, including the classic "The horror… the horror," both works stand alone, and Apocalypse Now! doesn't need to be compared at any stage with its less-popular inspiration.
To address the low-hanging fruit. Cats, the musical by Andrew Lloyd Webber, took the poems of T. S. Eliot (Old Possum's Book of Practical Cats) and created something new around the music, costumes and dancing aspects of the musical medium. When it was adapted to the big screen, only trying to dial-up with the tools of the medium (CGI and famous faces), the joke made no sense… for anybody. To be fair, no fan ever asked for this.
After all, this is what artists have been doing since forever. The less faithful, the more parodic and disruptive, the better. An adaptation that is not adapting, carries no responsibility with the original. The newer version brings its own voice and is a reflection of its times. This is the way Homer's Odyssey has been able to inspire great works from Joyce's Ulysses to the Cohen Brothers' O Brother, Where Art Thou?. This is not a change in the DNA that will give us an assured ill-version of the same thing. This is a complete transformation and evolution. Sometimes the result is awful, sometimes it is excellent, but at least it is a new thing. The only truth is that it is never the same.
There might be a hundred and one reasons why we ask for these inbred adaptations, but the main factor is that it is a symptom of an industry. In the same vein as sequels, prequels, spin-offs and remakes. The moviemakers keep feeding us with these descriptions of delicious dishes, and we keep telling ourselves that we are full and satisfied with a meal. When we wish for film adaptations, for whatever reason we might have, we are dismissing everything we love from the original.
If you still believe this is book snobbery, just think when was the last time you heard "the novelization was far superior experience compared to the film"?