Part of it may have been the dippy little keyboard
that it had, or the fact
that it only came with 1k or RAM (standard). If it had a larger keyboard,
instead of the tiny plastic membranes, then the idea *MAY* have caught on.
I wonder if ther'd be some way to either put a new keyboard on it (say,
from a laptop), or somehow make it into an expansion unit for something
like a TRS-80, almost like a CoCo cartridge.
As I recall, replacement keyboards were a fairly standard "accessory" for
the ZX-81. Ususally the idea was to remove the circuit board and drop it
into a larger case with a real keyboard.
The magazines at the time also usually printed sets of plans for taking
some kind of surplus keyboard (TI-994A, etc.) and reworking it for the
Sinclair.
That, and the odd company making keyboard overlays to give a more real
feel.
<<<john>>