Their target wasn't just tablets, but any device with a touchscreen and/or a small screen. As a Netbook user, I loved Unity and was excited about the Gnome 3 shell. It seemed like the logical progression of Ubuntu Netbook Remix.
What changed is that display and battery technology got better. I went from carrying around a tiny PC with an undersized keyboard (remember the Eee PC?) to one that weighs less, has a full size keyboard, and sports a display larger than the one the came with my first desktop computer. On this hardware, a traditional desktop environment feels cozy, while Gnome Shell feels foreign.
I owned one of the later models of the Asus EeePC and let me tell you, Gnome 3 ran like a old dog on it. Totally unusable. I don't know how you could use it. The processor was awful, the screen resolution tiny, while Gnome was a CPU hog and wasted screen space the eeepc simply didn't have with spacial bloat of interfaces evidently designed to be fat fingered on touch screens the eeepc didn't have.
What changed is that display and battery technology got better. I went from carrying around a tiny PC with an undersized keyboard (remember the Eee PC?) to one that weighs less, has a full size keyboard, and sports a display larger than the one the came with my first desktop computer. On this hardware, a traditional desktop environment feels cozy, while Gnome Shell feels foreign.