In "The Veldt," why is the children's virtual room called a "nursery" instead of a play room?

The term "nursery" suggests a place where the children are raised, not kept entertained, which is why Ray Bradbury's word choice in "The Veldt" is extremely important. David McClean, the psychologist George and Lydia calls to diagnose the room, directly spells out this idea: "This room is their mother and father, far more important than their real parents."

This idea of the nursery as parent is the reason why the children's loyalty toward the room is complete, while their parents consistently disappoint them. Throughout the story, the narrator reveals how the children had drifted away from their parents in general, but particularly when they introduced the nursery to the house. The parents consistently let the children down. They tell David that they let their children down when they wouldn't let them go to New York and then when they shut down the nursery for a few days until the children finished their homework. 

Finally, as a child would when someone threatens his or her actual parents, Wendy and Peter defend the room completely. Sensing the threat of losing the nursery, their primary caregiver, they lure their mother and father into the magical room where hungry lions are waiting to eat them.