Most 2-players perfect information games (Chess, Go, Checkers, Shogi, Hex, Hive .....) allow resignation and actually encourage it when the situation is hopeless. The only game in this category that is ususally played out is Othello because (1) it is anyway limited at maximum 60 moves (2) the discs differential is used as a tie-breaker. It is however allowed to resign also in Othello, just marked as a 64-0 loss.While it's true that I haven't taken part in a chess tournament, I have played chess enough to know some of the etiquette, and I know that recognizing you are beaten is a part of being a good player.
I also have played or watched other games and sports tournaments, where it's considered bad form to just leave the game even though you are beaten, because as I stated in my previous post the points you score may be taken into account for ranking you at the end of the tournament.
There is not a one-size-fits-all solution, but from what I have seen, more tournaments seem to follow the principle that a game should run its course to the end than stop early because you are beaten, and probably what the admins had in mind when designing the tournament system.
So I would strongly encourage to allow resignation also in tournaments, at least for 2-players games. If the score is used, we can assign the worst possible score, as in Othello.