Because Smith's teams were almost universally better than the teams they were playing against. And when you are better than the teams that you are playing against shortening the game is stupid. If your team is better than the other team you want as many possessions as possible, because fewer possessions means more variability (think Villanova - Georgetown).
And it was also criminal because the four corners isn't basketball, it's anti-basketball. If people want to see a dribbling exhibition or a passing exhibition they can go see that. Oddly enough, pretty much no one ever does.
Who was the only person who could hold Michael Jordan under 20 points? Dean Smith. And if you can't see how stupid stuff like that was, well, I don't know what to say.