> Yes, it is courtesy not to waste other people's time. Not sure where the controversy is, rather than your misunderstanding. Usually it's quite evident whether the game is lost (again, if you are a somewhat competitive player).

My experience from many years playing LoL and other competitive games is that it isn't. I can't count the number of times everyone wanted to surrender and then we clawed it back and won. Worse is that these are usually THE funnest of the matches since.