What kind of gear oil for 8 3/4? Why not synthetic gear oil?

Living in the past strikes me as ironic.
Aren't we all living a little in the past here?
I mean, this is an antique car forum.
I always run Mobil 1 in my engines.
And I know from fixing planes that synthetics have advantages in some applications.
But if there has to be a big discussion about whether or not to even use synthetic in a hypoid gear box, doesn't that raise some red flags?
Are rear ends failing that often? I think not. It's worked well for how many years with conventional oil?
Is a gear box really subjected to the same conditions as a internal combustion engine?
Are the break down,contamination and corrosion protection requirements even remotely the same?
Seems to me this is one of those "it ain't broken, don't fix it" subjects.
That's all I got.
Except this.