They just seem kind of pointless - people don't crash into your car on purpose so what's the point of the sign if it isn't going to stop people crashing in to you?
Is it a 'smug parent' thing?
Is it the excitement of sticking it on when you have your first child?
I have no idea.
But I do have an idea for a sign that ALL mothers should be given as they leave the hospital and it reads something like this ...
MOTHER DRIVING CAR
I haven't had a proper night of sleep in three years, my kids are screaming in the back and I am simultaneously trying to pass them back some food, find the song that they want on the Play School CD and steer the car.
I'd drive carefully if I were you because I'M NOT CONCENTRATING AT ALL!
How's your driving since you had kids? Mine is completely crap!