Shakespeare and Language

There are a lot of classic authors, and lots of books and lots of movies of books. Some of these books are written by Shakespeare and some aren't. Yet for some reason every time an adaptation of a Shakespeare play is released, it has to remain faithful to the original in terms of dialogue, and no other author is extended this courtesy.

Some examples are quite extreme. Baz Luhrman's film version of Romeo and Juliet and Geoffrey Wright's adaptation of Macbeth are both modernised versions of their respective plays, changing many concepts to their modern day equivalent (eg Macbeth becomes a gang leader instead of king, and the Montagues and Capulets are rival business empires rather than feuding families). Despite this, the dialogue is taken directly from the original, which sounds more than a little odd, having people in familiar modern day settings talking like shakespearean characters.

Done, I think, much better is Steven Moffat and Mark Gatiss' Sherlock, a modern re-telling of Arthur Conan-Doyle's Sherlock Holmes stories, interspersed with the odd original story. The first episode of the last series was a faithful modern adaptation of A Study in Scarlet, and the first two episodes of the upcoming series are based on A Scandal in Bohemia and The Hound of the Baskervilles. All are set in modern day England but the dialogue has been modernised with the setting. Yet the adaptation is very faithful to the original in terms of plot.

I'm on the fence in the usual book/movie adaptation argument - I appreciate that you sometimes need to change elements from books to make them work on screen. For example, I support Peter Jackson's decision to omit the entire 'Cleansing of the Shire' section from Return of the King because it would have spoiled the pacing of the movie. That said, sometimes things go a bit too far - many of movie adaptations of Roald Dahl books change things for no good reason and ruin the spirit of the original story (eg The Witches). I guess this is all a matter of opinion though, and therefore a slight digression from the point.

Basically: why is it that Shakespeare's language is immune from any kind of Hollywood meddling, even in a supposedly modernised adaptation, and that of other equally skilled wordsmiths (ie Tolkien) isn't? Shakespeare was indeed a literary genius, but he's hardly a special case and we need to stop treating him like one.