I can understand the sport analogy. But debates arent like football for example. If a team doesnt show up, then the other team wins right?
But in a debate, they are both trying to prove a point. If one person leaves the debate, they lost the opportunity to prove a point. But unlike football, when there is no counter point or contender, you dont automatically win, you just say what point you have said that goes uncontested.
Its like king of the hill, if you start it and everyone leaves, you arent "king" of the hill, you are just a person on a hill. You have neither lost or won, you just climbed a hill.
I hope my reasoning is making sense to ya, ill try to explain as best im able.