What is the wisdom behind the the unseen nature of Paradise and Hellfire, and the inability to imagine them?

Allah made this worldly life a realm of trial and tribulation. If Paradise and Hell were part of the perceptible world, then the trial would not be realized, and all people would believe, just as happens upon seeing the major signs of the Hour or at the moment of death, when faith no longer avails. This is because belief in the unseen is the fundamental distinction between faith and disbelief. A person can imagine Paradise and Hell, and indeed, the divine texts contain descriptions of them that bring them closer to the mind. Nevertheless, the blessings of Paradise are greater than what souls can imagine, in confirmation of the Qudsi Hadith (definition): "I have prepared for My righteous servants what no eye has seen, no ear has heard, and no human heart has conceived."