With the cameras and lenses of the 1960s, creating the convincing illusion of a thousand-foot-long spacecraft required a fairly large miniature. The 11-foot Enterprise model weighed 225 pounds -- not exactly easy to swing about on a wire rig. It was simply more practical to shoot the (mostly) stationary miniature against a blue screen while the camera tracked, panned and tilted. It also meant that a library of stock Enterprise shots could be composited against different backgrounds, which probably saved money in the long run.
I do wonder, though, how live-action model shots of the shuttlecraft might have looked if Trek TOS had engaged the talents of top miniature FX men like the Lydecker brothers or Derek Meddings.
I wonder how the 33-inch Enterprise model might have looked on wires, in front of paintings. For brief shots, as an addition to the 11-footer and not a full-time replacement, it might have been fine. Just don't show the underside of the saucer.
Not only was the 11-footer too big to put in front of paintings, they say it was too big to photograph in a versatile way, period. Or the fx studio space they had was too small. If the 11-footer were in a larger studio, they could have put it in front of a black curtain with lit pin-holes for stars. You could put a physical planet model in the shot. It would either look "wonderfully organic" or cheesy beyond all measure. Don't know which.
Derek Meddings was amazing. His diorama sets often fooled me completely.
Three cool pics from Superman II:
Superman II windy street:
Superman II farmhouse:
The scene above looks brighter and sharper than the CGI of today. Boy does it look good.