Look the person who said it was stupid: They were old, they have had this dog for 13 years, maybe they didnt want another dog because they might die when owning this dog and it would have to go to a shelter. People who lose children often go into depression, the dog was like a child to them. They maybe didnt know how to handle their dogs death, maybe they have seen to many friends die (they are old), maybe it wasnt just the dog, maybe the dog was just the last straw.

So it is not stupid. I admit it is not clever but it was their way of handling their grief.