A player who resigns matches or times out can change the whole outcome of a Triple Gammon tournament.
It's okay if they do it for everyone but when they only do with a selection of players it adds 5 points to the lucky ones (or the friends in the case of manipulations), whereas those whose matches with them have finished will have gained nothing, a single point or maybe 3 or only rarely, the backgammon's full 5.
Timeouts cannot be prevented but resigning matches is not an option in TTTs unless the player withdraws completely.
To prevent a player from spoiling the tournament, the TTT rules remove a player who inadvertantly or deliberately adds dollops of points to people's scores in this way. They may continue to play out the remaining games if they wish, but they and all their games are no longer part of the tournament (whether that's total removal or just not contributing to the scoring).
playBunny: Playing without this rule makes it pointless to have tournaments under this format, since it will almost always be the case that someone in such a large group will time out, resign too soon, etc. Now that you've pointed it out, I'm going to cancel the triple gammon tournament I just created recently.
alanback: Moreover, the slower you play, the better equity you have to collect points due to timeouts / resigns. It could lead people to play as slow as possible. It could be a general rule in all tournaments that when somebody timeouts or resigns a backgammon, he or she automatically forfeits all games with maximal scores, even the already finished ones.
nabla: What if a player is legitimately going to get backgammoned and resigns. The system would need to handle that. Or worse yet, what if a player is likely to get gammoned, but not guaranteed and resigns. How do you score that?