Children play with toys. You did when you were a child, and so did your parents before you. We like to spoil our children, and so we feel inclined to go out and buy them the latest and greatest in playthings. There's only one issue with that; very young children have no concept of what's supposed to be a toy and what isn't, nor how much money you've spent trying to entertain them.
Children take a while to develop a sense of danger, and when they're young the whole world around them is theirs to play with. Sometimes that can take the form of cardboard boxes, as if they were cats. Other times, it will take the form of something potentially dangerous. They don't understand why we're telling them off, but these are valuable lessons to learn.