Anyone who has boys will understand this.
Especially if your boys like to walk around outside in their socks, which get all muddy and black, and then put their shoes on...thus transferring muddy and black material to the inside of their shoes, and consequently to all future clean pairs of socks so it looks like I don't do laundry.
We have discussed this many, many times at our house, especially when I am trying to clean out the inside of a certain boy's shoes, as I was this morning.
Me: "Kyle, let's try not to get the inside of your shoes all dirty. Can you do that?"
Kyle: "It's not me, it's the sand."