For what it's worth, I didn't fly the '73 first; I flew a series of turbo-props for my first years of commercial airline flying, followed by the BAe146, none of which had auto-thrust. I then changed airline and went onto the A320 - my first auto-thrust aircraft.
I took to it like a duck to water - my background is in electronics, and I very soon understood the way the engineers had designed the A320; it seemed very logical to me, (once I had understood the side-stick logic).
I was used to scanning the engine instruments, which we should all do anyway - even with moving levers - so I found it no bother at all.
Why don't the levers move? They don't need to, the auto-thrust is very good and it is very easy to see what the engines are doing, and Airbus innovations such as groundspeed mini, mean that the energy is retained, and the aircraft is almost always in a safe place energy-wise. The auto-thrust works very well, (apart from older A330s being "lazy" on convective approaches, but which is easy to correct), so I trust that it will do the right thing for me, and if the speed decays or increases more than a little; I just flick my eyes across to confirm that the auto-thrust is commanding the engines correctly.
By not needing to move in auto; the engineers were able to design a series of thrust lever gates to easily and intuitively command the different phases required: Normal, Flex, Max continuous, TOGA, all the while keeping the option of conventionally and intuitively going to manual thrust if required. I found it relatively easy to operate manually: just watch the speed and adjust as necessary - just like in your car, you can easily keep the speed right by watching only the speedometer and the rev-counter.
Yes, the levers could move in the CLB quadrant, and the MCT quadrant during OEI operations, but that would add a lot of unnecessary complication with motors, clutches, feedbacks, jams, and runaways and all sorts. Also, pilots would get used to feeling the levers and would not monitor the N1/EPRs. Airbus encourages us to scan properly, which is no bad thing.
After 12 years the airline I flew for went into administration. I could only get a job on Boeing 737 freighters - the Classic -300/400.
I found the automatics of the '73 quite crude, and having to have PM's eyes inside the cockpit setting the thrust during the start of the take-off roll and a go-around struck me as very unsatisfactory and safety compromising.
After a season of the '73, I thankfully got a job with another Airbus FBW airline.
Just my take
