The problem is that, by leaving only a few pennies, the wait staff will think you are a total a-hole and won't even stop to consider the fact that 1) you were unhappy with the service and 2) they will have no idea as to why you were unhappy.

In other words in the long run it accomplishes nothing. Would you go back to that restaurant and expect good service from the same wait staff next time? You're more likely to find something in your food.