I don't understand?
Just because you don't think about it being in your purse means it doesn't offer you protection should you need it?
Put it this way:
She kept a pen in her purse. Its always in there, but she never needs it. In the rare event that she DOES need it, she has it available to use. Would she always be thinking, whenever she went somewhere, 'oh, I have a pen in my purse!'. No, because its ALWAYS there. You don't think about it.
Because she wasn't trying to sneak it in. If she was, she would have worn it, and there is no check for that.