>It's extra silly since there's always a robust aftermarket for any reasonably popular car.

One difference is the difficulties in making some 'parts' now. It's one thing to make a fuel pump for a 1950's car, quite another to duplicate a controller board, often with obsolete parts and secret software, that runs the convertible top.

Another is that a lot of parts are more monolithic than they used to be and harder to design/build. Look at headlight assemblies.

It doesn't help that with the increasing amount of software and electronics in a modern car (a Tesla being the leading example), the auto industry is acquiring the product lifecycle times and forced obsolescence of the PC industry.