That the babies are able to play on their own. The Babies are able to eat and drink on their own. The babies are still spending much of their time in the nest box. The babies still stay near their mother. They need light to see by.
Light keeps rabbit from getting bored and depressed.
Lighting is essential for reproduction in the winter months because of the length of the days. Rabbits need light to find their water and feed bowls. It can cause a buck to go sterile. It causes the buck to get bored. Bucks love hot weather because they get lots of does to breed.