Actually there's no such thing as "running up the score". Sometimes one team is just head and shoulders above the other team in talent, or just happens to be playing a better game on that particular day, and that usually results in a lopsided final score. It is unnatural for athletes to not try their best when they're in the game. What's a coach supposed to do, tell his players "don't try to get another hit, or don't try to score another touchdown, or don't try to make another basket"? For those who would say put in the second or third string players when you have a big lead, sometimes even those players can't help themselves from playing well and scoring more points.
Actually there’s no such thing as “running up the score”.
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Of course there is such a thing as running up the score. A Big East coach was accused of it recently. He was waiting for the opposing coach (Patino of Louisville) to send him a signal and start putting in subs. But since Patino didn’t do it the coach (I think it was the Notre Dame coach) continued rightly with his starting five. Certainly he was not to blame there and Patino agreed.
Coaches expect players to try and score but they do give them instructions which make it difficult. In football a coach will run the same play up the middle encouraging the opposing coach to put 9, 10 or 11 guys up front to keep them from making yardage and eat up the clock. Of course the opposing coach must be careful. A guy like Paterno would run two of those plays and then throw an 89 yrd bomb.
In soccer, teams that are ahead by several goals put in defensive players to keep the losing team from scoring but also to keep their own team from scoring.
It use to be if you were the coach of a team that ran up the score you would have been condemned by the media and the fans. That was true until around the 1970’s when the Miami Hurricanes did it on a regular basis. That’s about the same time sportsmanship in sports died.