Here’s an article called “Why flipping through paper-like pages endures in the digital world” that unfortunately doesn’t look at the answers in any kind of interesting way. Especially since it hasn’t “endured” so much as it’s making a comeback.
Whether developers recognize it or not, users still subconsciously desire some kind of visual feedback when flipping through multiple pages of content. Some of these visual cues are comically exaggerated (iBooks), some are more subdued (Instapaper’s “Fast Pagination” action) and others fit somewhere in between (Flipboard). But each presents a challenge to developers attempting to blend the tactility of real-world pages with the digitally native tablet aesthetic.
Developers do realize it, which is why they (usually) build it in. And the desire isn’t subconscious—if I can’t immediately tell that a page has changed, I am very conscious of the confusion that creates and the half second it takes me to examine the text to make sure it’s different than the text I just read. Personally, I like a quick page-to-page fade, or the iPhone Kindle slide effect. Page transitions that mimic actual books are kind of ludicrous. McLuhan would hate them. Or love them, I guess.
The point is this: we once moved from scrolls to books, so we shouldn’t be all that shocked that we’re moving from scrolling to book-like page transitions. What makes it more interesting this time around is that we don’t actually need to. Though in the case of reading on my iPad, a slight right-to-left twitch of my thumb is vastly easier than scrolling the entire length of the screen from bottom to top, so maybe it is the same thing.