old guard fan

Why do we have this so-called " 2 points per week block rule ". After watching guards for the past 20 years, it almost seems that the top 4 or 5 units in each class is already determined by the end of February. I'll agree that with practice a show should improve, but why should a score change 6 points for a show that is performed the same, ( or in some cases, worse) just because it is 3 weeks later ? I will agree that it is impossible to have a perfect, impartial scoring system when you have people evaluating a performance, not a finish line to cross or points to score. Why can't the judges evaluate what is front of them that day alone, not based on how they did 2 or 3 weeks ago, or who the staff is or how long they have been in a class ?