Because they didn't have decent computers in the 1970's
and therefore could not calculate capacitor values to the
bitter edge of near failure.

Of course they decent computers! Ever seen an HP-35? My aunt gave me one as
a pre-graduation present, and I was one of only three people on the U of MD
campus (out of 35,000) who owned one. Several of my dorm-mates were science
or engineering majors, and we'd sit around of an evening, using the HP-35 to
calculate the answers to their homework.

Frankly, even a slide rule is accurate enough.


Designers weren't quite sure what they could get away with,
so they always left a safety factor.

They still aren't sure. No responsible engineer designs a circuit to the
hairy edge of proper operation or reliability. (I know, I know...)


There was also an odd preception that electronic devices were
supposed to last "a lifetime". It was not unusual to have TV's
and consumer electronics last 20-30 years without anything
more than mechanical failures.

I've been lucky. I have tons of electronic equipment, and most has held up
with hardly any breakdowns. This includes recent purchases. * My NAD MR-20
lasted 20 years of heavy use until the focus went out. (If the parts were
still available, I would have fixed it. Ditto for my 36" Sony flat-face
WEGA, which also gets heavy use, and is nearly 10 years old. I expect it to
go at least another 10 years without repair (if I keep it).

The least-reliable products I've ever owned came from one of /the/ leading
American manufacturers of high-end audio. /Every/ component broke down
repeatedly. When one of the power amps damaged one of my speakers, that was
the last straw. The replacement amplification, designed by John Curl and
costing much less than The Other Spread, has given no trouble.

The "throw-away mentality" is most-likely due to the rising cost of
competent service bumping into the falling cost of electronics. Not to
mention that the latter are increasingly difficult to service. The rapid
changes in technology also encourage people to throw out broken stuff.

* Of course, I rarely buy cheap products. Purchases are permanent
investments that "ought" to last forever. This has mostly been the case.