Yes it is a waste of time to look at "what if" hands. If you fold 72 and the flop is 772, you have to ask yourself what the odd are of this happening? Over the course of a year, 72 has a negative expectation so you fold it.

The whole idea of poker is the fold/check/bet/raise based on positive expectation (At least in limit holdem. In NL holdem you have to play the opponent more making NL a lot tougher).

It's also useless to check the "rabbit" card which is another "what if" scenario. If there are 44 cards left, then the top one has a 1 in 44 chance of being any particular card. If you were looking for an ace and there were three left, then there is a 3 in 44 chance that the top card is an ace. What's the point of looking at it if the hand is over? Do that 44 times and 3 times it will be an ace, so what?