Why was the little boy not afraid to climb the wall?

The little boy was playing make believe.... he didn't realize that he could get stuck, and the tunnel was just wide enough to get through. Unlike fairytales, however, the jagged coil was unyielding.

Next day he pretended to be the Prince who braves the terrible thicket of thorns to enter the palace and kiss the Sleeping Beauty back to life: he dragged the ladder to the wall, the shining coiled tunnel was just wide enough for his little body
to creep in, and with the first fixing of its razor-teeth in his knees and hands and head he screamed and struggled deeper into its tangle.

In addition, the boy's mother waited until he couldn't hear to voice her worry.... the little boy was never warned.

The wife said. You’re wrong. They guarantee it’s rust-proof. And she waited until the little boy had run off to play before she said, I hope the cat will take heed The husband said, Don’t worry, my dear, cats always look before they leap.