Why did they quit using this logical excellent means of simulating flight in cloud?
At a guess - expense?
At my club, when I did my IMCR training we used screens, which were angled to give the instructor outside vision but the student couldn't see anything. I would think that the two stage amber would probably cost more than this, or possibly be timeconsuming to remove/reinstall (the aircraft used for IMCR training were not exclusively so).