Why?

This will be brief, but is an observation that has built up over the years. Namely, for some reason the boys really like stepping on/standing on our feet. Why is this? I happen to have noticed it lately because in two separate incidents I have injured toes on my left foot. And since then, I have found myself spending an inordinate amount of time and effort trying to keep them out of the way of little feet that are intent on finding them and applying maximum painful pressure. I am never fully successful either, they always manage it. What's the impulse? I know that they enjoy causing me pain, they've said so. But, knowing this, I've intentionally hidden the injury from them. I think maybe there is a claiming thing going on, but maybe it's a desire for closeness. Injuries, personal space issues and shoe care aside, there's something pretty nice about 2 little creatures for whom an inch away would be too far sometimes.