Not wanting it is one thing, but why sell below value?
Typically, the elderly parent or relative lived out in the boonies and the heirs live somewhere "better" and not close by. The heirs don't want that old house, and it's vacant, vulnerable to squatters, vandals, critters. There's probably no insurance. It hasn't been kept up. The lawn needs care, the snow needs removal. The heirs simply can't be bothered. It's not worth it, in their eyes.
PS: If the elderly owner is in a nursing home and Medicare or Medicaid is footing the bill, the house is going to belong to the government anyway. All the heirs get is the liability, every day it’s vacant. They are very motivated to get rid of an old house for peanuts.