Emphasis mine.
That is what I meant - I think people care about the fluff in the main campaign setting books, and I would include the primary rule books (PHB, DMG and MM) in that category.
The splat books are definitely more about the crunch, which is what they are all about, and will now be marketed as new "modules" to add on to the basic rules of D&D Next. That is my thought.
Everyone buys the primary rule books, not everyone buys the splatbooks. Therefore, the primary rule books have to have some flavor / fluff that is recognizably "D&D".