very rarely do you fold KK vs AA preflop i can only think of 2 scenerios
1. Its a satelite tournament you have KK, your just about ready to claim your ticket as you have a great stack .. and your raised all in preflop.. its best to just fold, and wait to claim your prize since the payouts are all the same.
2. The player has been very tight, and not rasing alot of pots preflop.. Then out of the blue makes a unusal all in raise.. Now if your up against a nit, and a really solid player who plays only premium
hands.. It can cause alot of warning signs that its ethier QQ / very unlikely possible JJ/ or a AK..
But KK is very tough to get away from, and its just bad luck to really get it in verus AA but it happens to everyone.