Almost all cars will be scrapped after an accident, and the remainder will rust after 20+ years
I don’t believe that is true. Most older cars are simply run into the ground, with less maintenance taking place (down the the bare minimum when you’re in banganomics teritory) until some slightly-more-expensive-and-critical problem emerges (clutch, DMF, cambelt, etc) and its simply not worth spending the money on fixing it and the car goes to the scrappy. Rust is an issue on pre-2000 cars, but most non-japanese things from the last 20 years are incredibly solid – I had a knackered old 2005, 200k mile signum (vectra) till 2022, it had no love in the last 5 years, but its bodywork didn’t have a hint of rust on it.