To add to the other answers, part of it is also etiquette. If the only way you could recover a game was your opponent doing a really bad blunder, at a rating wh

To add to the other answers, part of it is also etiquette. If the only way you could recover a game was your opponent doing a really bad blunder, at a rating where such blunder is very unlikely you should simply resign. Obviously, you have to take the whole situation in consideration. If the position is very tricky, you would play on even anyway. If your opponent is low on time, then it depends on your opinion on "dirty flagging". This only applies to the top, as a +3 advantage is definitely not a guaranteed win unless you're at least a titled player.