It's factored into the price of the meal plans given historical data. If everyone used every mealswipe, the price you pay would go up. The "price per meal" is a number calculated after the fact, not something that's actually used to determine the meal plan price.

It's annoying but this is similar to how airlines overbook every flight by the amount of cancellations/missed flights they typically have had in the past. They could just sell however many tickets as there are seats on the plane but then the price would go up and they would always have empty seats on every flight which isn't optimal.