A fourth theory is that would-be Android tablet buyers are simply slower on the draw than iPad buyers. They didn't jump onto iPhones in that device's first three years but waited until Year 4 (2010) of the smartphone phenomenon to join in. They'll wait out another stretch before buying a tablet because it's still too early to go there.
Google's own behavior may encourage such slow motion: It made devicemakers wait a year after the iPad to get its own tablet OS, causing many vendors to release ill-advised smartphone-based devices for the holidays. Even now, its pace is glacial in updating and releasing Honeycomb. Google has also made no effort to outflank Apple, following Apple's lead in almost every area instead (voice-based search and navigation being the major exceptions).
The theory that makes the most sense to me comes fromt Doug Dineley, InfoWorld's Test Center director: Android tablets aren't competing with iPads, but with laptops and netbooks. An iPad is a computer, with lots and lots of apps that do real things. iPad users tend to see their tablets as "+1" devices to carry around for communicating, Web surfing, entertaining, and some work -- but most have their PCs or Macs at home, at the office, or at the hotel room for heavy-duty tasks.
Netbook owners usually view their devices in the same light, and some even have decent battery life, reducing concerns about charging the computer at crucial moments. Certainly, iPad haters have been known to sneer, "Why use an iPad when you can use a real computer (a netbook or laptop)?" If they really believe that -- I suspect they do -- then the same complaint applies to all tablets.
In fact, in the last week I heard exactly that from many of the RIM fanboys upset that I bluntly criticized the BlackBerry PlayBook tablet for its many failings: It's OK, they said, that the PlayBook doesn't do very much or very well because, after all, that's what a computer is for. Windows tablet fanboys (yes, there are some, mainly in government) say the same thing.
Maybe those attracted to the iPad think different about computing, and those who think different about computing are attracted to the iPad. Those who see computing as the same old same old and tablets as basically keyboardless laptops won't go for any tablet, even if they love their Android smartphone (or BlackBerry).
That would explain the vast gulf between Android smartphones' success and Android tablets' landing with a thud, even with attempts at iPad differentiation such as sporting a (buggy) Flash player and, in what All Things D's Walt Mossberg calls a "parlor trick," 3D, as seen in the $750, 9-inch LG G-Slate.
A smartphone replaces a cellphone, not augments it. A tablet augments a laptop and rarely replaces it completely, unless you view a tablet as a compromised laptop. If that's the case, the Android tablet makers have a big problem. It's a good thing many of them also make laptops and netbooks.
This article, "The Android conundrum: Why tablets tank, smartphones surge," was originally published at InfoWorld.com. Read more of Galen Gruman's Mobile Edge blog and follow the latest developments in mobile technology at InfoWorld.com. Follow Galen's mobile musings on Twitter at MobileGalen. For the latest business technology news, follow InfoWorld.com on Twitter.