Coloring Outside of the Lines!

One day I was coloring with my niece and she said to me "oh Tessa, your picture is so pretty.  You did a good job coloring in the lines...but why?  Do you have to color in the lines?"  After my 4-year-old niece's brilliant discovery to thinking outside the box and not following society norms, I ask you, do we have to color in the lines?  Do we have to teach inside the box?  I hope my teaching will reflect my niece's abstract thinking of coloring outside the lines.