It tempers predictions. Like, for example, when every fan board thinks they improve by 5-10 games for the next year. We know this won't happen and we can identify the culprits most likely to not fulfill this. If the usefulness of projections and analysis is limited by being 100% accurate - someone should let Parker and every other baseball commentator know they're wasting their time. It's a rather unfair bar to hold anything to. The funny thing is we hear these kinds of objections when there is pessimism about the favored player/club. But if someone were to post the same projections that say we can expect better from Nolasco, Mauer, and probably Perkins? Well, hell, regression to the mean is awesome then!