What are the Universal Physical and Metaphysical Laws of Laundry that indicate that whenever one carries an armful of laundry from point A to point B, part of said laundry (usually socks or underwear) will jetison from the armload to land on the ground partway along the journey, which you then have to make a second journey to come back and collect?

Perhaps, I can understand why socks carry out this sort of behaviour, being the rebels of the World of Attire, as evidenced by the ability of one of any given pair to dissapear in the washing/drying process (presumeably run off to live in a paradise where socks are free to be as dirty and smelly as they damn well please). But underwear? And the other occasional garments, just jumping overboard for no apparent reason at all?