Houses had thatched roofs, thick straw pile high. It was the only place for animals to get warm, so all the pets, dogs, cats and other small animals, mice rats, bugs, lived in the roof. When it rained, it became slippery and sometimes the animals would slip and fall off the roof.
This is also the reason why four poster beds developed. The idea of the ‘roof’ was to keep from nasty things falling into your open mouth when asleep! The side curtains kept out the drafts.