So they can miss the winter, when their food supplies disappear. Bears hibernate because their food supplies disappear in the winter.
Hibernation is the way bears adapt to nature, and survive the harsh winter weather.
When the temperature drops in winter, most wild animals have trouble finding food. Some animals stay awake during the winter and search for food and shelter. Bears choose to spend their winter in hibernation. Hibernation is a sleep-like state. During hibernation, bears cuddle up in a cave or hollowed out tree.