I did not think there was actually a rule about when you can forfeit. For example, if you unscrew your cue during your opponents turn, it's counted as a forfeit, which took place in the middle of the opponent's inning.
I have often conceded the last ball to someone if it was easy (9 or 10 ball here), or even if it was semi-easy but they had a good run out to get to it or a good position shot or something. If I respect the player and we have a good match going I would not want to see someone miss a game winner.
In fact, several times I have people concede the game winner to me when I felt iffy about making it. Took a load of my mind let me tell you hehe.
I take it you don't gamble? You would never see this mindset with players gambling.