Now, I could come up with the reasons that resonate among the experts these days: email and Twitter are training folks to read short and quick. No longer do readers, especially the younger generations, want to take the time to savor the words, immerse themselves in the word pictures we create. Books being published these days have to grab the reader with the first line or paragraph, open with an action-packed scene, and keep the reader totally engrossed in the story from beginning to end.
The explanation given is that readers don't have the time to allow the story to grow in their imaginations; they want something that gives them instant gratification.
I just read a blog posting by an experienced writer/author who's been in the words-producing business a long time. In it, he gives the lowdown on why the changing taste of readers has impacted his style of writing. He says it a whole lot better than I can so go to http://venturegalleries.com/blog/why-readers-want-to-read-a-lot-of-white-space/ and read it for yourself.