It has to do with modularity and commoditization. Modern parts can be highly integrated and digitally customized to specific applications, in such a way that th

It has to do with modularity and commoditization. Modern parts can be highly integrated and digitally customized to specific applications, in such a way that they become increasingly scarce and eventually impossible to find, whereas older cars are mostly made from commodity components where the same part is interchangeably used in tens or hundreds of vehicle models, and many become cheaper and easier to obtain as time goes on and tooling costs are amortized over decades.