Why should car companies re-invent the wheel, or for that matter the distributor cap?

Years ago, I had a '63 Sunbeam Alpine. Front shocks were about $100 in 1979. I took one to an auto parts store and they let me look through their inventory. Shocks from a Chrysler Newport were an exact match. $8 a piece.

Why should we be surprised if something from a Mercedes is interchangable with a cheaper make? Is a parts supplier such as Bosch going to make two different parts or try to sell the same thing to two different companies?

My uncle was a sales rep for a carberator company with a sales route in Wisconsin, Michigan, Indiana and Illinois. He sold the same design to a major motorcycle company, two snowmobile companies and a farm equipment company. The price difference in replacement parts was amazing.

I'm sure you can find many interchangable parts if you look. Actually the stupidest example was that the same GM alternator was priced differently depending on the way it was clocked. Take out the four long bolts, turn the mounts 90 degrees, put the bolts back in and the $29 alternator became the $89 alternator.

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1983 300SD "Guderian"
1987 MR2
2015 Camry
2015 Chevy Spark
2006 Hyundai Tucson