By Pool, I take you are referring to a game of 8-ball (there are many variations of billiards games). As for your question, there are a few different ways that a player can foul on the eight ball. When fouling, the advantage is that the next player has ball in hand, allowing them to place the cue ball into a favorable position. So I would gladly have the player just tap the eight ball, as it increases the likelihood of leaving the cue ball in a favorable position for me to win the game.
Take a look at the rules for 8-ball to get some of the other specifics regarding fouls, etc.