Trenta is meant for watery beverages that are relatively lower calorie than the milky expresso based beverages and Frappuccinos. The idea is to be a little bit socially responsible and not encourage overindulgence. Yes, you can add vanilla sweet cream cold foam or heavy cream and lots of syrup to a trenta iced coffee or tea or refresher and make it high calories, but, in general the principal, the policy makes sense when it comes to a 31 once iced beverage.