Really it still exists today, it is just not as obvious. I have a friend that used to work for Honda R&D. They would come up with a good way to do something and the higher ups would say no because they could use part X from another vehicle to do the job. Yes it might be more complicated and result in stupid placement of a part that requires an arm with 4 joints to change a bulb but, the part already exists so they must use it. The problem is that it is not well documented. For example, the HVAC box in my 2000 Acura Integra is exactly the same as a 97-01 Honda CRV or 00-06 Honda Insight. The cool thing is both of those cars have cabin filters and mine doesn't. (So I added one.) Granted it is not 40 years but, there is just one example that goes across 12 years at least (94 Integra RS-06 Insight). There are many more examples (b series engines, k series engines, subaru engines)