It's been years since Amazon's Kindle was introduced in 2007, yet no one cares about e-readers. Three years after the iPod was introduced, it had taken over portable music and was already in its fourth generation. Three years after cell phones were introduced in the early 1980s, they were still too expensive to afford -- but everyone wanted one. We thought we were cool and living-in-the-future just to be able to talk on a cordless telephone outside our house. So why will e-paper never come close to replacing real paper?
First, we should consider another big failure of digital-only media / entertainment -- video games that are downloaded onto a memory stick or hard drive, rather than ones that come on a single disc or cartridge. Virtually none of the major games are gotten this way, although the technology allows it. People want a physical copy of a single game. The only somewhat popular use of "downloadable content" is to provide a few bells and whistles to a game that you already have a hard copy of.
In the biggest mistake in Sony's life as a video game maker, they changed their handheld system, called the PSP, from a system that took individual discs to one where everything is downloaded onto a memory stick (the PSP Go). This is exactly like going from a portable CD player to an iPod, yet it has done pathetically -- no one is buying it or wants to buy it.
What is the difference between recorded music on the one hand and video games and books, magazines, newspapers, etc., on the other? For iPod owners, they are listening to single tracks, not entire albums. They're flitting from one song to another (typically by different artists), rather than getting immersed in the fullness of a single album. When you play a video game, though, you don't want to play one level on this video game, then another level from another one, then a third level from yet another game, and so on -- you want to get into a single game for a decent stretch of time. The same with reading a book: you don't want to read five chapters from five separate books, but rather as far into a single book (or maybe two) as you can when you're on the metro, lounging around Starbucks, or whatever.
The main appeal of media players that can read a ton of digital files off a single small memory source is their portability -- with an iPod, there's no need to lug around 20 CDs when you only want to hear one song from each. (That means those albums stink -- only one song worth listening to? -- and that you should find better artists, but that's another topic.) In contrast to single songs, where most people want to zip from one to another across albums and artists, no one tends to bring 20 video games with them during a single session of handheld video game playing -- one or two will do fine, and they're already pretty small. Ditto for books: no one tends to bring 20 books, as just one or two or even three will do, and they're already fairly easy to carry around. Thus for video games and books, no one cares about greater portability -- the ones we carry around are already portable enough, being so few in number.
There are certainly other reasons why digital-only video games and e-books suffer, like how not having a more durable copy of something makes you more vulnerable to losing it, and gives you nothing to re-sell in the secondary market if you get bored of it or don't end up liking it. But that's true for mp3 files as well, yet most people are fine with it there. There's something different about how people experience single songs vs. video games and books, namely how immersed in a single long work you tend to get, which determines how many hard copies you tend to bring, and that makes portability worth it or not.
The one thing that could have saved e-readers from oblivion is if magazines and newspapers had only existed in print form. Articles from periodicals are like single songs -- most readers zoom across a bunch of them from a host of sources. Even those who follow just one newspaper are really reading multiple newspapers -- one unique to each day. If you wanted to recall earlier articles in print form, you'd need to hold on to all those old newspapers or magazines. Here, lack of immersion in a single copy would make portability a huge attraction.
However, newspapers and magazines screwed themselves over by putting everything on the web -- for free no less, though that's not going to last beyond next year. So, all you need now to read periodicals on the go is something with web access, such as an iPhone. That's really all that e-readers could offer, and they're much less portable than smartphones, so they have nowhere to go. The reports of ink-and-paper's death are greatly exaggerated.