Good students getting into grad schools have been beating "the odds" all their life, so why should it continue to be any different? . . .[W]here would one have ever gotten the message that being at the top of the heap and the class will eventually not continue to open whatever door you knock upon? The first real rejection these people (like many of us) have ever experienced is from their job apps.
That's a good point as far as it goes. If you're going to grad school, you're probably used to being better than most of your classmates, if not all of them. Your experiences up to that point in life probably don't prepare you all that well for thinking clearly about the job market--especially not years before you hit it.
At the same time, in philosophy there really are clues out there for people with eyes to see. There's the Leiter Report, for one. You apply to a range of schools in the top 50 and below, and you only get into schools below the top 40. There it is, staring you right in the face: you are no longer the top of the heap. I guess it's just hard to take that on board.