> Now we're being told the opposite.
The choice of unusual film standards has always been to make the film a bit "special" when viewed in a suitable cinema.
The original format 1.33:1 was simply using 35mm wide film (originally 1.35") and after putting sprocket holes on each side, there was 1" of usable width, and someone decided to make a frame 1" x 0.75". The projected image was just scaled linearly.
When they started adding audio, the image was shrunk slightly to 22mm x 16mm (the ratio of this image was modified slightly to 1.375:1), and the audio track was just placed between the right hand edge and sprockets. They could use the same projector technology, just with a mask between the film and the lens so that the audio track didn't appear on the screen, and an optical pickup head for the audio that was placed below the mask and lens.
As an aside - a silent movie projector has a complicated gear system that advances the film 4 sprockets in a jerk, once every 24 times per second, while before and after that it is fed smoothly (so you have a "loop" of film above and below to take up the slack). You also have a shutter that closes for half the frame to hide the film when it's actually moving, and open when it's stationary. When the audio passes the audio sensor after the bottom loop, it's moving linearly, so the amount of light that can pass through a narrow slit is proportional to the voltage sent to the speaker. Later when stereo was added to films, they just fit 2 audio tracks into the space of one, so mono films would work on stereo projectors and vice versa. And even later, Dolby surround was encoded as a dot matrix pattern in between the sprockets (actually, it was just a film ID and timecode that was encoded) and the audio itself came from the 3-5 CDs that came with each film. But I'm getting ahead of myself.
These two standards stuck around for quite a while and then some of the later experimental TV systems started also using this ratio, probably to making filming non-live TV possible / easier as they could use the film process and show it on a TV using a telecine without wasting any of the image space.
Once TVs started to become popular, directors started wanting to make their films more special, something that couldn't be experienced the same way on a TV. And so began the arms race on picture formats. For a while 1.66:1 was popular, which used the same projectors as before but changed out the lens for an anamorphic lens which squished the image to make it wider. And soon, 1.85:1 was standardised (with a different anamorphic lens and mask). This was known as "flat" and was used by the majority of films. Some of the higher budget films were produced in 2.35:1, known as cinemascope or just "scope" and so now most cinemas had 3 sets of masks and lenses - square, flat and scope - and could show pretty much everything with a pair of projectors just by swapping the lenses. A few special aspect ratios were tried, but these were usually limited distribution to specialised cinemas, and cropped to a standard size for regular cinemas. In this era, usually the curtains could move to the correct width for each film, or fully closed.
70mm film has been around for quite a long time, but never really caught on as it was expensive to shoot - non standard cameras, roughly 4 times the area of film (and so at least 4 times the cost, but more because demand was lower), and limited where it could be seen as most projectors were 35mm only. It was possible to get projectors that had a swappable gate so you could also show 70mm film, but they were relatively rare - probably less than 10% of cinemas had these. The aspect ratio was almost always 2.2:1, and so while it was narrower than scope format, people would pay extra for the 70mm experience because of the higher quality (and less grainy look).
In the 1990s, TVs started shifting to 16:9 (1.77:1) which was a half-way compromise between improving the quality for films (1.85:1 scope doesn't need to be cropped much or only has small bars top and bottom) and leaving masses of unused space for older 4:3 TV broadcasts. However 16:9 was never used for cinema, and more directors switched to 2.35:1 for films after that to keep the "better in cinema" quality.
So personally, I don't think 1.43:1 is really any better for 70mm (after all the film is so much bigger, the quality is already improved), rather it's almost certainly been chosen so that it looks different, and much better at cinema. Just as films shown in "letterbox format" on TV with half the screen black looked bad on a 4:3 TV, now pretty much every TV is 16:9, watching a 1.43:1 film on it will have big black bars on the side and detract from the experience. The cinema will be the best place to watch this.
So, IMHO, it's all just a marketing gimmick aimed at those that want to pay a premium to see a film as the director intended it.