Not that many years ago, there was a significant amount of worry from people in the PC world. There was a new, disruptive marketplace segment that threatened to wipe out the PC world entirely. The tablet takeover is all but irrelevant now, and PCs remain (in one form or another) completely dominant for serious work in many (perhaps even most) professions.
Why Use a Tablet?
First of all, it's probably worthwhile to first discuss what problems the tablet was suppsed to solve.
Tablet computing was meant (as far as I can tell) to bring about a new revolution in computing by bringing a bigger screen to the more intuitive touchscreen interfaces. I don't think it's very hard to imagine why somebody would want this. Teaching someone new to computers how to use a mouse takes time, no matter how small that amount of time is. Ths time could be better spent teaching someone concepts such as design language in user interfaces, or what types of websites to avoid. Mousing around can be quite frustrating for a beginner, but by the time tablets were taken seriously, capacitive touchscreens had improved enough that they could be used to deliver actually compelling experiences all their own. It's natural to pinch to zoom, it's like stretching fabric, and you don't generally need a hint on screen to tell you how to do it. On the other hand, I'm not sure what portion of the popultion knows about Ctrl + and Ctrl -, but I'm pretty confident it's not 100%, or even as widely known as pinch to zoom. There's a lot of human factors involved in why this is, so intuitively it makes sense to push for this type of design. That's what progress looks like.
So, the smartphone revolution happened, starting with the iPhone and cascading into Windows Mobile 7, the Zune HD, Android OS, and even (briefly) Blackberry OS. There were (and are) others, but these are the major players from the early days.
Given this new revolution of friendly computing you can carry in your pocket, it made sense to scale this up to something bigger. We had been reading the news on our computers for ages, but a phone screen (still) is a little too small for many people to be comfortable using it to read the Times. The result was an immediate race to make the biggest and best tablet interface. Again, this more or less kicked into full gear with Apple's solution, the iPad.
Less than Excellent, Less than Last Time
This time was a little different, though. The major players (for the most part) took a phone interface and scaled it up for a tablet. Android 3.0, iOS, and Windows 8 all took this approach. Out of these, Windows largely went back to focusing on desktop, and Android went back to investing in the phone OS. Android still has a presence, as does Windows, but they're both relegated to budget offerings, where the iPad virtually dominates the high end of the market.
Basically the only one of the thre of these to keep continuing to focus on a tablet interface in any meaningful way was Apple, and it shows. Android and Windows still offer tablet features, but both of them have kept their focuses on their original markets, respectively. More accurately, Android has never kept its focus on tablets, and Windows has opted to focus on 2-in-1 PCs over tablets.
This has left us with Apple, Amazon's Kindle (basically the last serious long-running Android tablet), and 2-in-1 PCs that run desktop apps. Google's Play Store will ususally give you phone apps that scale poorly to larger screens, Windws apps scale poorly to smaller screens, and the iPad is left as the only really polished experience.
Far from the revolution that was the smarphone, this time around we get a scaled up version of the phones we already have, or we get a lot of upset PC users over Windows 8.
Bad Email Device?
Typing on a tablet can be awkward. I'm writing this article on a Surface RT with the included touch cover, and while vastly better than using the touchscreen to try and type, it's far from a real keyboard and I mess up a lot more than even on my worst laptop.
Phones get away with this due to their size. You can comfortably use your thumbs to type on the screen and get reasonable speeds that way. I think it's fair to say that the typing speed ceiling is far higher on a full size keyboard, but that doesn't make the phone terrible at typing. Then there's desktops and laptops. Both of these have a full size keyboard that (usually) give you individual, full size keys and a plethra of hotkeys to use with them, making the experience for keyboard users actually pretty good. Even Windows 8 could be operated comfortably from the keyboard without thinking too hard about it.
Tablets, on the other hand, have a screen size that makes using thumbs to type a little awkward, since the full device is much bigger and heavier than a phone, but they're often too small to put a full size keyboard on screen; even when they're big enough, they rarely even try since half of the benefit of a full size keyboard is raised keys to aid in touch typing.
The best solution that I've seen is on the Surface with the type cover, but then you're basically sitting down with a laptop and a stand. That's putting aside the fact that you're getting the touch cover with the $500 base surface, which doesn't even feature an Intel CPU. That's far less of a burden if you can at least install your own apps, but Microsoft's play during this era was to offer a tablet that only allows Windows Store apps. For a similar price you could get a much more capable laptop with a touchscreen and have a better in-lap experience anyhow.
So while Ballmer's infamous soundbyte about the iPhone may seem funny now, had he been talking about tablets he may have had a point.
So do they Suck?
No*
Tablets were never going to take over the PC market, and it's silly to think so in hindsight. The mouse offers so much more precision, and serious business usually requires a keyboard or something similar for conversations over email.
Tablets are very good for reading things online, however, as well as in-car movies and light gaming, like Solitaire.
This may seem kind of obvious in hindsight, but it's why the tablet revolution never came. Even for professions that now have the iPad Pro for their work, such as graphic design, there are lots and lots of industries that never got their tablets. Nobody seems to target the engineer or software developer with a tablet. It's widely preferred in these fields to have the precision and utility of a mouse and keyboard, and tablets sre specifically designed to remove the complicated options and precise input of a mouse in favor of a more intuitive touchscreen and fewer confusing looking ports on the side of the device.
I feel like I should mention that this is in fact (very slowly) changing with the iPad. You /can/ do serious work on it in video and sound production, or really any artistic field that makes use of the pen. It's become a very cool /option/, and options are good. Furthermore, this iPad seems different with its keyboard case, similar to what the Surface attempted to do so many years ago.
But that's it, that's my take on why the tablet revolution never came. Now to stop typing on this stupid touch cover and go back to my model M :)