Part of your reasoning was "just to see if he was serious". And that if he has less than an ace he is likely to fold. Well I agree that if he has less than a pair of aces he is likely to fold. But the problem is here with KK you beat everything that is less than a pair of Aces. So you don't want him folding the hands that you do beat. However, if you raise and he calls you have pretty much manipulated villains range of possible hands to hands that you are now behind (because he folds out the hands you beat). But if you were to just call then on the turn he still has hands that you beat in his range.

To look at it in the simple and traditional sense. A bet or raise should get worse hands to call (so you get value) or get better hands to fold (as a bluff). Well here you fold out the worse hands (less than a pair of aces), and you get called when you are behind.