Hindsight may indeed be 20/20, but it takes a true stranger (or dear friend) to hand us the heart of obviousness on a silver platter, garnished with a generous helping of unintended vitirol.
In those moments when we find ourselves sitting in the ashes of our most recent personal holocaust, the last thing we need is for somebody to shove in our faces that most obvious summation of what we have been beating ourselves over the head (and stabbing ourselves in the heart) with for the duration since...
But it somehow seems to be human nature to need to do so. Is it a need to be helpful? A need to say "hey, moron..." or "I told you so..."?
This most likely only continues to be done because usually it is delivered to us in a state where we are too personally crushed to leap up and throttle them, thus saving this trait for continuation in the gene pool.
Perhaps it is merely fate's way of grounding us in our hubris, much the same way that returning Roman generals were accompanied by people who would remind them of their eventual fates...