I think gg has basically become a way to remind your opponent you have surrendered and therefore the game has ended so they can now either accept your surrender or watch their history now they know it's ended.GG is also used to suggest to the opponents you have won and they should surrender which itself is quite arrogant and insulting.I would be interested to know the first warlight game was said.
GG is not just a thing affecting warlight it has been ingrained in all our game cultures and has persisted for over 10 years now as the earliest definition of gg on urban dictionary was on 2003 so therefore something that has gone on for so long on warlight and other games and is neither deadly to the game aside from being annoying to people can not become stopped easily especially considering now it is common courtesy to reply gg to someone or say gg.
http://www.urbandictionary.com/define.php?term=gg