A/A obviously is the best possible hand you can have Pre-flop, but that does not mean that it will always pay dividends, Depending on my position on the table, and has there been action before me, I will consider many more hands to enter a pot with, I have even played 7/2 suited from the BB because most players folded around to the BTN player who then just limp's in, Had he raised Pre-flop I might have considered folding a 7/2 suited or not, because they could be playing any two better cards with the same suit.
Players are sometimes blinded by their hands hitting big on the flop, Like A/A making trips on a A,Q, J, flop, but many players will play K/10 from some positions, and of course if you don't see the board pairing, your 3 of a kind will not beat his Straight. Also if the board does pair, what is stopping your opponent from having Quads? So you need to be cautious playing any hand.
Poker is so much more than a simple game of cards, You need to be cautious in some circumstances, Bold in others, but above everything else you need a good read on your opponent and know when you are beat!