Problem was, you were doing it a heck a lot more often. Oil changes: 1200 miles. Spark plugs, points, condenser about 15,000 miles. Ignition wires distributor cap and rotor, about 30,000 miles. Tires and drum brakes 12,000 and 15,000 miles respectively. Wheel bearing repacked, chassis lubes and tires that flat spotted in cold weather. Then there was the miscellaneous repairs, generally all before 50,000 miles: Exhaust, shocks, generator/alternator, carburetor rebuild, starter motor, u-joints, heater core, water pump and all the belts. And while diagnosing problems did not require a computer, it still required mechanical/electrical knowledge and a few gauges and/or meters.
Most cars today will go 100,000 without touching anything mechanical other than brakes. Oil changes are now based upon how you drive and can be 3,000 to 7,000 miles. And when something goes awry, a little "check engine" light pops on to tell you something is wrong that you didn't even know about! No more guessing either. They plug in a computer and the computer tells you "Replace XXXXX" and you're good to go.
And don't get me started on the safety differences. People walk away with a wrist sprain from accidents that would have killed them back in the 'good old days'.
I love old cars (speaking of which, the Woodward Dream Cruise is only a few days away) but today's vehicles are vastly superior in every way to the oldies.
To those who complain about repairing a used car: go price a new one and you will sing a different tune!