They lost the slide projectors on the overhead monitors because of the cost...the number of union operators required was too expensive.
That's sad. If I had to make a bridge, I would want every type of display. Plasma screens, rear projectors for a soft light, LEDs LCDs, a little bit over everything to add layers of warmth to the images.
That would be great, but in the 1960s there were only CRTs and rear projection screens. CRT monitors would have been unwieldy and expensive, so rear projection was the only real choice.
Then there would have been the continuity problems as pointed out above.