The text of Ray Bradbury's 1950 short story entitled "The Veldt" provides many clues as to why Wendy and Peter focus their attention on the African veldt.
Bradbury's story is futuristic, imagining a time when houses do everything for the inhabitants. In this case, the HappyLife Home cooks, cleans, bathes, entertains, and takes care of every aspect of daily living. The children have a nursery that reads their thoughts and brings their imaginations to life, complete with three-dimensional visuals, smells, and sounds. Lydia and George Hadley have catered to their children's whims in every way. When they become concerned about the nursery, they divulge the children's obsession with it to the reader. Consider this exchange between George and Lydia, in which George is asking his wife to lock the nursery:
“And lock the nursery for a few days until I get my nerves settled.”
“You know how difficult Peter is about that. When I punished him a month ago by locking the nursery for even a few hours — the tantrum be threw! And Wendy too. They live for the nursery.”
“It’s got to be locked, that’s all there is to it.”
Later, George is reflecting on his decision to purchase the HappyLife Home system and thinking about how it works. He hints as to why Wendy and Peter would be conjuring an African veldt—they are thinking about revenge and death.
"Remarkable how the nursery caught the telepathic emanations of the children’s minds and created life to fill their every desire. The children thought lions, and there were lions. The children thought zebras, and there were zebras. Sun — sun. Giraffes — giraffes. Death and death. That last. He chewed tastelessly on the meat that the table had cut for him. Death thoughts. They were awfully young, Wendy and Peter, for death thoughts. Or, no, you were never too young, really. Long before you knew what death was you were wishing it on someone else. When you were two years old you were shooting people with cap pistols."
George and Lydia begin reflecting on the things that have gone wrong. George repeats a proverb that says children are like carpets—they must be stepped on occasionally. He reflects that he and his wife have never lifted a finger to correct their children. He admits to his wife that the children have become insufferable, and points to several examples in which they as parents had to say no for safety reasons. Their children's requests have become more and more outrageous. The parents call in a psychologist who explains that the purpose of the room is to analyze children's neuroses and then provide treatment. His recommendation is to immediately close the nursery and bring the children to him every day for treatment.
But Wendy and Peter have become addicted to the nursery, and virtually estranged from their parents. They know that their parents are the only thing that stands between them and the nursery. They have set a trap to dispose of their parents in the nursery, in an African veldt.