David Megginson wrote
That's what one would hope. Unfortunately, there are many gradations
between CAVU and IMC, and pilots do seem to have an unfortunate
tendency to fly into mountains or get stuck in canyons from time to
time while (legally) VFR.

Some people fly to the legal limits of the certificates and ratings
they hold; others do not. I realize this is obvious. What should be
equally obvious (but sometimes is not) is that in order to do so with
a reasonable margin of safety, you need a much higher level of skill
and knowledge than what is required to pass the checkride.

What we're doing here is exploring one tiny corner of the knowledge
envelope in great detail. Most pilots couldn't care less. Most
pilots are also not going to fly in the mountains in anything less
than good day-VMC, so they really don't care - or need to.

The examiner is not able to check every possible knowledge area in
depth - that's not his function. He only performs a rough check to
make sure the instructor didn't leave out anything really major.
Anything else would take much too long.

So really, all you need is a few people who don't know what they don't
know and pay the ultimate penalty to observe what you've described.
I'm not sure if lack of knowledge of temperature errors has ever
caused someone to fly into an obstruction he thought he was clear of,
but I can certainly believe it has happened.

Michael