There are several reasons. The largest is not what you likely imagine. The biggest change in internal combustion cars of today versus something from the mid 1990's or older is actually the engine, and more specifically, the metal casting techniques.
Older stuff used basic green sand castings. These molds tend to align rather poorly. The outer mold is just compacted oil sand. If the part cannot be cast with green sand using a cope and drag, they used inner cores that are made of chemically hardened sand. All of this is manually aligned and has poor tolerances. One of the causes of poor tolerances is the tendency for the mold and core to shift. The molten metal is a liquid and the sand parts float on this liquid, like a whole lot of floatiness.
Newer techniques use better chemically hardened core like materials, and instead of using green sand with a cope and drag, the entire mold is made of hardened sand that locks with multiple pieces like a puzzle that cannot come apart. This technological shift is the main reason why cars went from lasting 60k to 120k miles to 250k to 500k miles.
Also investment casting is now used on many smaller parts. Basically a wax version of the part is made. This is coated in several layers of a ceramic slurry. Then it is fired in a kiln, burning out the wax and leaving a ceramic negative of the part. The form is placed in sand and then cast. The ceramic is far far more accurate, but is a labor intensive and more involved process.
From my experience in auto body work, owning my own shop, the way cars look is primary down to metal forming machinery and the quality of steel. The thinness of the metal sheet and its strength dictate much, but it is also a compromise in how easily the panel can be assembled on a line. Limits in logistics complexity management are also a critical factor. One of the biggest shifts here in the last twenty years is the use of adhesives and robotics. Adhesives have replaced fasteners and welding in many places on modern vehicles. It is one of the reasons they are so resilient in crashes. This is nothing like the adhesives you find in the US consumer market. These are on the level of fucking dangerous if you stick your fingers together or get them on a hand. They are not taking a thin layer of skin off or letting go like anything you are likely to have used before. These are only available in industry or at an auto paint jobber. The ability to form complex bends and metal drawing operations without cracking the steel sheet are key. Like as a body guy, I am looking at how the panel was initially formed, and then the exact series of forces that went into crumpling and damaging it. My job was to create as close to the same amount of force as possible but in order, and in reverse. Over time, the complexity of forces used to initially form every panel has increased. So when I look at cars, I see this progression of industrial technology and materials.
In other words, six fender washers and three frame bolts cannot compete with fifteen glued panels and complex geometry under the thin surface you see outside. It also makes new cars unrepairable in most circumstances. They are, but not in a traditional sense that passes classical insurance standards. It requires… creativity… like an, artist. (Do not look behind the curtains.)
The actual argument for old cars is ownership.
OCR tool+ to autogen a suggested alt text. The path of least resistance needs to be lowered.
Alternatively, inverting the paradigm is likely to cause less issues and push back. Add the automated tool the the end user in need of the version. This obviously creates the issue of data quality and trust, but for the smaller group. What if there was a reply field silently posted to everyone’s notifications feed indicating anonymous instances of the tool being used to fill in the gaps for alt text? The message would need to be opt out or carefully presented. Perhaps it could be possible to modify the post itself via the tool? Better yet, make the alt text field a Wikipedia style affair anyone with an account can edit, but with a lock available to the OP. That would create much more healthy awareness of the need for alt text, as people posting the content will see the places where gaps are filled by an automated tool. It gives them the chance to edit. This does little to initially improve the experience of the most active alt text users, but it creates a strong cultural shift in awareness that should improve the situation greatly in the long term IMO.