There could be several reasons why cats sleep under the bed. For example, cats are naturally wary, and the space under the bed provides them with a sense of security—it's an instinctive drive. This is especially true for cats that have just arrived home; unfamiliar with their surroundings, they might choose to hide under the bed for protection.
Secondly, cats might choose to sleep under the bed for fear of being punished by their owners. When a cat does something wrong, it might hide to avoid being scolded by its owner until the owner calms down. This demonstrates the cat's intelligence and ability to read people's expressions.
