Why couldn't they just follow the book?

I know, it's one of those "the book's way better" threads, but seriously, I'm genuinely curious about the decisions made here.

Extreme Measures by Michael Palmer - the book - is riveting, suspenseful, and twisting. I'm curious, why did they need to change it so much? It's one thing to make it a Hugh Grant vehicle by changing the main character from an Armenian named Eric Najarian to a Brit named Guy Luthan. And I guess I'm okay with changing the setting from Boston (really important 'character' in the book, though) to NYC. But all of the other changes made the movie and book almost unrelated, beyond the broadest plot of "driven, brilliant doctor finds out about some unethical yet potentially critical medical research."

All the sub-plots about the 'facility' in Utah, the dive instructor and her brother, the neurotoxin -- those made the book quite good and unique. I don't know how replacing them with a generic NYC facility and Sarah Jessica Parker sped up the plot or made anything better. Plus, you lose the central twist in the book - there is no mystery in the movie.

I'd love to see a remake that actually follows the book some day.