If everyone says gg automatically without thought it runs the danger of not being sincere. When I say gg after a game, my opponent knows that I genuinely believe it - I think it is more important to say good luck, or similar, at the beginning of the game.
Saying 'gg' after a game
Even at OTB tournament I only shake hands before the game. I reserved any figure of speech as I do not wish my opponent to have the impression that I'm trying to distract him/her from the game.
I had a bad experience once when I tried to be nice and greeted my opponent with a warm handshake while saying "Good luck". He chided, "do I need good luck to win over you?". It maybe a joke but since then onwards, he just went cold throughout the game. Food for thought.
Saying 'gg' after a game is good thing to do as it shows that you are sport.
A player who won a game and the other person who lost ask for a match but didn't say a 'gg' can be seen as rude. Yes there is chess etiquette that we should practice to do.
However isn't a bad thing as well that the person who won ask for a 'gg' and saying 'no gg, no rematch'
So what do you think about the last sentence?