It's all in the laws of physics and the center of gravity. Without the top strap, the basic supporting shape would be an upside-down capital L, and things would just fall over. You'd need either some support underneath and away from the body (to shift the center of gravity under the... objects
) or you'd need a very sturdy side support to prevent it from falling over at all... which may or may not be comfortable, depending on who the maker of the strapless bra in question is.
Ermmm.... what were we discussing again?
