I think it's for the same reason that "It was all just a dream" is such a terrible plot device.
There is a meaninglessness inherent in the retelling of a dream. You know at the outset that it didn't actually happen, so why is it interesting?
There is a meaninglessness inherent in the retelling of a dream. You know at the outset that it didn't actually happen, so why is it interesting?
So now I have a question for you: what is your personal stance on dreams?
There is meaning in the person considering the dream meaningful enough to tell it.