We don't?
I bought King of Dragon Pass (a-sharp.com/kodp) and Teudogar and the Alliance with Rome (teudogar.com) for the dialog. And look at the interactive fiction (text games, Infocom style) community: they're going strong, and have four or five major authoring languages.
Of course, those are 'indie' titles / freeware and the majority of shelf games involve little to no actual dialog. But that doesn't mean world-building and story-crafting are any less relevant. Some games I've loved just because they told the story well without cluttering it up with words. So I do agree that 'game writer' is a rather silly and non-relevant title. I'm saying that game designers wear a huge number of hats, and one of the hats is a writing hat, and is often neglected.
Gromnir, I agree that looking at paintings doesn't make you able to paint, but all great painters (barring bizarre exceptions) have looked at paintings. And the craft of writing is most certainly taught in schools. Isn't this what being an English major is all about? The how-to-write section and the literary criticism section of my local Borders (combined) are bigger than the philosophy section, and nearly as big as the history section.
I'll check out the books you've posted about. A bigger library is always a good thing. Thanks.