Besides, most cars are worn out before they would die of age, at which point it's not worth the money to repair it.
The problem is that the wear out design limit went from 50+ years to 5 years. This is a throw away society. Stuff doesn't stick around long enough to break most of the time.
There's a reason our 1960's farm truck is still running strong with the original engine and every vehicle that has come along since the mid 70's is in the junk yard - including the ones that were given the utmost care to avoid breaking them. Repair vs replacement costs? Let's see here, one time cost over 40 years ago for ancient reliable with routine fix-it costs vs $20,000 every 4-6 years when the new thing falls completely apart and has to be replaced.. the old truck is, um, like free at this point with a pile of replacement cost money that never had to be spent.
Are we talking cars? No automobile was ever purposely engineered to go anywhere near 50 years. For all the reasons Option listed as well as exactly how long would an auto company stay in business if they did this? You might not like it but companies do need to make $$ and selling a person one car in their lifetime won't do it.
My 60's car looked like this in the 70's.

It was an exception to the rule in that it even survived that long. Bumpers falling off, fenders flapping and your feet punching through the floor boards were common.
When shopping for used cars at that time you figured at 50,000 miles there were going to be repairs, 75,000 meant serious repairs and anything near 100,000 wasn't even considered.
Having recently shopped for an inexpensive used car I can tell you now there are loads of cars out there with 100-200,000 miles that are running very well.
I commuted (3+ hours a day) in 1960's cars up until a few years ago. Safety is non-existent compared to modern cars. Unpadded steel dash boards, poor braking ability and a single master cylinder (nothing says wake up like one of those failing

) maybe lap belts (maybe not they were an option or unavailable in early cars), and steering wheels that you could pretty much tell would break in an accident and send the center post punching through your chest. Like motorcycles, driving such cars is a calculated risk, not one many people would choose over modern safety features.
Reliability may or may not be there. Betting your lively hood on an old car getting you somewhere everyday can be sketchy no matter how well you maintain it. A part breaking can mean weeks, possibly months of scavenging. It isn't easy for a typical person to have that luxury or the fortitude to keep up the battle. You do it cause you love to drive something like that, not because it is practical.
But anyway, back to Hondas. When I decided to move on from commuting in old cars I bought a used '98 Civic GX, a CNG car. Wasn't really for the convenience of a newer car as it was for that precious HOV sticker that came with it.
