“MUCH HAS BEEN WRITTEN ABOUT the quaint and lumbering buopoths native to the Exilic Lands and other curious places – but to this day, little remains understood about the shy beasts beyond the proverb that ‘they will haul all day on a fatberry-cake and a kind word.'” — from Road Bound
That’s the in-universe explanation from one of my Prosatio Silban stories. Outside the stories, it’s a different matter entirely…
According to H.P. Lovecraft‘s 1927 novella The Dream-Quest of Unknown Kadath (a ripping good read if you’re so inclined):
In former dreams he had seen quaint lumbering buopoths come shyly out of that wood to drink, but now he could not glimpse any.