[ortek_service]

I imagine the main problem is that 'scope CRT's needed to use lower max. deflection-angle electrostatic X / Y plates, for wide bandwidth rather than 110deg TV deflection coils. And so you need a much longer neck relative to screen size, making larger ones not very practical.

I was surprised there was a 12" one, but looking at that Airmec one it isn't too deep, and does have very-low 10kHz bandwidth.
- It seems it was intended to be a Schools demonstrator unit, rather than a particularly good proper 'scope.

I recall there were later-on in the the 80's all-digital TV-Scope add-on units, to use a TV as one (but with much reduced bandwidth etc.)
And once solid-state 'scopes became Digital-Storage only, with no direct analogue mode, then you could have a much larger built-in conventional CRT monitor built into it - before they finally switched to widescreen LCD's.