The problem with your theory, at least in my case, is that I knew why I wanted a portable mp3 player before I ever had one. I saved my pennies to get that first Jukebox. And with the first iPod, I was like, Perfection! (although it would be until 2d generation before I could afford one.).
The same with iPad, although it still doesn't really function the way I want it to. It is the best option, however, and when it came out, miles beyond anything else, like the iPod.
The iPhone, of course, was truly revolutionary.
The wearable I want is something akin to a TNG communicator, plus the Enterprise computer, plus a floating display a la Star Wars.
Alternatively, they could build in watch functionality into a watch band that I could attach to my existing watch, using its crystal as an HUD. But even then, it would mostly be a toy kind of thing, with limited utility.