Well yesterday morning I was sitting in the office reading, listening and waiting for the dryer to stop. I had intentionally left the bedroom door open because I knew I would be returning there with a basket of fresh clothes in a couple minutes.
My little J raced past the office, sprinting into my bedroom. I gently reminded her of the rule by calling out, "J. Where are you going hon?" She walked to me and answered, "Oh nowhere, Ma." To which I prodded further, "What are you doing my J?" She made her intentions clear with, "I'm not going in your bedroom to put lipstick on my lips, Ma. I not do that. No no."
And this is why we have the rule, and keep the door closed.