http://www.bandsman.co.uk/brass013/msg00930.htm
"I have come across three general reasons why the oboe has been
historically used to tune the orchestra.
The overtone structure (number of harmonics as well as their relative
strengths) is more similar to that of the strings' in that there are far
more, and of greater individual intensity, than that of the other wind
instruments. A greater percentage of the acoustical energy of a given
note is distributed throughout the harmonics than of the fundament.
This allows the strings to match up their overtones with those of the
oboe more easily than with, say, the clarinet or the flute. The flute,
for instance, (and similarly the organ pipe) have relatively few and
quite weak overtones - nearly a pure sine wave. This is why pipe organs
have numerous ranks of 'lingual' (reeded) pipes to balance their
'labial' (open) pipes, and have entire sets of 'tierce' pipes to
individually reinforce the octave, fifth, seventh, etc. overtones of a
given fundament pipe.
The second reason I've heard is that 'back in the good old days' when
woodwind technology was not as good as it is now the tuning range of the
oboe was far less than in contemporary instruments. Thus the oboe,
being relatively fixed at one pitch, was tuned up or down to by the rest
of the orchestra. I can't, however, personally vouch for the accuracy
of my information on these limitations to the early oboe.
The third reason is related to the first in that, as a result of the
timbre of the oboe, its sound 'cuts' through the general hubbub of the
orchestra and can therefore be heard by everyone in the room.
Interestingly enough, the characterization of the oboe's sound as being
the "purest' is diametrically opposite of what you would expect by the
use of that term. A sine wave is by definition a pure note: 100% of the
acoustical energy is in the fundament. The oboe sounds like an oboe
precisely because it has a greater percentage of its acoustical energy
distributed amongst its harmonics as compared to its fundament - check
it out with your pocket spectrum analyzer. Assuming, of course, a good
player; otherwise it just sounds like a duck! (wry grin)."
The oboeist must have to tune to something---if not an electronic tuner, then a tuning fork, a piano that's been tuned starting with an electronic tuner or tuning fork? Oboeists aren't expected to have perfect pitch are they?
It would make no sense for an entire orchestra to tune to the instrument that has the most difficulty staying in tune---which is clearly not the oboe. Musicians have to adjust their instruments during a performance when they hear themselves off a bit----if the instrument they tuned to has gone off more than anyone else....yikes! A chain is only as strong as the weakest link. Thus, if you tune to your "weakest link" you will have a very weak chain.
I completely agree----it is not "rocket science".