There is no upside to running up the score. None; at any level. Professionals, in particular, do not do this unless it is payback. The coaches and players respect each others efforts and abilities too much.
If you are way ahead, play your bench. If you are way behind, play your bench. No matter who you are, or what you do, you will eventually meet someone who is better (and even the best get beat). If you haven't experienced both, then you simply have not lived long enough.
Holding down the score in a lopsided game is called good sportsmanship. People who exhibit poor sportsmanship, as well as those that exhibit good sportsmanship, are remembered for their actions. Reward and/or payback for both types of behavior can come in the form of tournament seedings, game times, etc. People that practice poor sportsmanship make life harder on themselves in the long run. The irony is that they cannot see very far down the road, and probably wouldn't feel any culpability anyway.
As a coach, I have never been on the losing end of a lopsided score. I like to think that some of this good fortune is attributable to how we conduct ourselves in victory, as well as defeat. As a player, I experienced lopsided losses in several sports. I cannot think of one time that this kind of loss went unavenged. All of the old, tired sayings are old and tired for a reason. In this case; "You reap what you sow".
