Sometimes shelters don't know, either because the dog came in as a stray or because the previous owner who surrendered him was not forthcoming.
Slightly off-topic: I have seen shelters that post a note with the reason the dog was surrendered and they are heart-breaking. "Old dog didn't get along with the new puppy." "Dog kept running away." "Vet bills are too much."
Slightly off-topic: I have seen shelters that post a note with the reason the dog was surrendered and they are heart-breaking. "Old dog didn't get along with the new puppy." "Dog kept running away." "Vet bills are too much."