people complain when people say gg and when they don't... its amazing how much power those two letters have
The problem is saying GG could also be interpreted as a mockery, especially with the advent of multiplayer games these last decade or so, where saying "GG" is a way to taunt your opponent - the all too easy GG EZ comes to mind. Now imagine your opponent just blundered a major piece or their queen, or walked into forced mate, and you say GG ... they could interpret it that way and think Im just trying to taunt them. So I normally stay silent in my games.
I believe that it depends on your mood to chat. Sometimes even a simple "gg" is too much chat for that particular day. I really dont think it has anything to do with somebody being rude or insensitive. If somebody sends me a "gg" I always respond back with the same, even if they destroyed me, or I beat them badly. But this is an interesting topic that you have brought up.