Metric System

Now, I've come to grips with the fact that we stupid Americans refuse to change over to the metric system. It just makes so much more sense. Whatever, we're allowed to be pompous. But here's my question. Why does soda come in bottles in liter increments and why do milk and orange juice come in cartons or bottles in quart/gallon increments? Seriously, today at the third meal, I was looking at a 2-liter bottle of Sunny-D (no, not soda or purple stuff) and right on the label it said 2-liters and in parentheses 2.1 quarts. I understand that such beverages need to come in plastic bottles with twist-off caps because their carbonation needs to be preserved, but what would be the big problem with having quart bottles or gallon bottles? If 2-liters and two quarts are almost the same quantity, shouldn't there just be one standard? If someone can explain this to me, I would be in his or her debt.