This is one of the biggest quandaries in Poker, It really does not matter whether it is KK,or QQ, or even AA. They all have the same problem and that is they are all beatable by other hands.
Sure AA is a massive hand but I have had it crushed by 8/10 off when the 8/10 hits a straight on the flop, when the chips are all-in pre-flop it all comes down to Luck! and it is that simple.
I once folded AA pre-flop simply because we were so close to the bubble I would have gone out if I had called, and after following the flop, turn and river I was correct in my reasoning,
I went on to pass the bubble in 160th place and managed to make the final table, so sometimes it pays to be cautious, It hurt me to do that but it was a necessary tac-tic.
All pairs are in a precarious position even when they make a set I have seen them beat by straights, flushes, 4 of a kind and the one lesson I have learned through playing thousands of games is "It is never over until the fat lady sings" The hand is not over until the River hits.
When the fun Stops, STOP!