Therapeutic Massage Chairs

Why do boys aged around 12 use their feet to play with their shoes?
I’m a teacher and I have always wondered why when boys are sitting down they often allow their feet to fall in and out of their shoes. Similar also to when they are walking around and their shoes aren’t tightened up and the shoes act loose like sandals. I think it’s maybe sort of like a therapeutic thing similar to someone rocking on their chair.
But I never see girls doing it although I have seen men in their 20s doing it occasionally.
I wonder if maybe there is some sort of phycology behind it, are they subconsciously massaging?
I think this would fall under the general category of “self-stimulation”, like tapping a pencil or drumming your fingers or tapping your feet to the music in your head.
Most boys are quickly bored by people talking and need to engage more of the nervous system in activity. Girls, in general, find talking much more engaging than boys. Even thinking, which is subliminal “self-talk” usually does hold most boy’s full attention.
Tim Clark Golf Pro speaks on Human Touch Massage Chairs