It was a trick post - now we know who all the old farts are...
I would have to say the largest contributing factor to today's automobile longevity is our government. Believe it or not, the Clean Air Act of 1968 is largely responsible. Electronic fuel injection and engine management came about only because the Fed made the manufacturers straighten up. Racing didn't advance technology. Geez, Ford beat the pants off of Enzo with stock blocks running Holleys. Now there's some high tech gear for ya...heheheh.
A major by-product of low-pollution engines is they also run cleaner internally. Less fuel in oil contamination meant better lubrication and less friction/wear, less carbon build-up yielded cleaner valves, etc. The ability of modern engines to 'tune' themselves while driving is phenomenal compared to automatic chokes and self-advancing, point-type distributors.
Now that the drive trains are lasting longer we couldn't have the bodies rotting off the tires, could we? New methods and techniques have made cars much less rust prone. Who remembers that the first stop for a new car was Ziebart? Who remembers the last time they saw a Ziebart?
Didn't the hp ratings change because of Mr. Unsafe with a comb and tie? (Ralph Nader) The ratings were based on engines that were stripped of all ancillary devices - belts, pumps, air filters, exhaust, etc. The new rating was called 'net horsepower', or the actual flywheel hp an engine would produce with all parasitic devices connected and functioning.
If I happen to be right I won't hold ya to the fries, my doc would kick my fanny if I plugged up all of this new plumbing.
Hmmm...not many guys came back from WWII, Korea or 'Nam carrying any extra weight. A lot of them remembered living (or should I say starving?) through the depression. Women that worked during WWII usually kept somewhat of a figure. Since then I think it's just become a slow slide into complacency. That and we'll always need someone to sing at the end of the show so we know it's over.
Beav