Why do none of the "Bourne" movies follow the original plot lines from the novels?

because the producers think that they can make more money by changing the original plot and since the bourne collection does not have that big of a book-fan base they can get away with it

With that being said--does anyone know of a movie that followed its book counterpart exactly?

some of the old movies actually did follow the books exactly like A Streetcar Named Desire, To Kill A Mockingbird

in recent years, the only movie that was an almost exact copy was the Da Vinci Code (it changed the ending a little bit)

High Fidelity is pretty faithful, beside resetting the story in America. In fact all the adaptations of Nick Hornby's novels have been really close.

I also think the the Bourne series, which were pretty much a Cold War era setting, wouldn't fit in our day and age. Plus, Ultimatum would probably be 9 hours long if it followed the book.

I second Glial on time, a book can cover a lot of ground that a movie just can’t represent in the 1.5 – 2 hour movie.

The genre facts of life are:

* Movies are different from books. VERY different.The mediums/genre differences are so stark that it’s almost impossible to adapt a book to film and be “true” to the book.

* Movie makers tell stories in pictures. Not everything in a novel can or should be represented that way.

* Movie makers try to stay close to the story intent of a novel and translate that intent in actions we can see. (Internal monologues, for example, are hard to show visually.)

* I when I go see a movie based on a book, I don’t go with expectations that the movie will “closely follow” the book. That’s because I’m familiar with filmmaking and know what a challenge that presents.

* I liken this to mapmakers trying to acurately represent the 3D Earth on 1D paper. The result is a distortion. When people see the actual size of continents (as opposed to what they are used to seeing on common maps and atlases), they are shocked—especially Americans. They can’t believe how small the US is as compared to other countries.