On the bus with me today were a woman and her son, who looked pretty big for his age, but since he was drinking out of either a bottle or a very tall sip cup, I presume he was no older than three or four.
Mama sits her son down on the frontmost bus seat, which is parallel to the sides of the bus, while she goes up front and chats with the bus driver during the entire ride home. While Mama is chatting with the bus driver, Sonny is a little wiggle-worm. He kneels on the seat, looking out the window and at one point stands up on the seat. In either of those positions, if he had lost his grip on the seat, he could have tumbled backward any time the bus turned left, because the bus tends to tilt in the direction it turns. Did Mama see any of this? No, because she was standing by the bus driver with her back turned completely to her child.
Now granted, it's unlikely that the boy would have been snatched from the bus itself, but any predator paying attention could take note of where they got off and figure the kid is easy prey because his mother doesn't keep her eye on him.
Somebody else on the bus made sure the kid didn't fall off the seat and made sure that, when he got off the seat while the bus was still moving--because his mother had told him to come to her--that he didn't fall down between his seat and his mother.
He got off the bus safely--but no thanks to his mother.