Finding Adverture

One thing we talked about in class was how fairytales often start out with a character being told not to do something and then always doing it. For example, Snow White would have never met her prince had she not gone against the dwarfs' wishes and allowed a stranger to give her an apple. This makes me ask the question, how you can read a fairytale to a child and then expect him or her not to enter the closet you firbid them to?