I am an iced coffee guy, especially in the summer. While getting one the other day, something hit me. Why don't they just serve them in a styrofoam cup with a different lid?

Let me explain my thought. The woman in front of me was automatically given a styrofoam cup to put her plastic cup in. That's 2 cups for one drink. Everyone wants it in the styrofoam cup. Even though i'm not quite sure why its needed, (how long do you actually need to keep it cold for), I understand what the point of it is. So, why not eliminate the need to use up 2 cups for one drink? Just pour the iced coffee into the styrofoam cup, use a lid that will allow the use of the straw and save cost and the envorinment at the same time. Sounds good right? Maybe there is an iced coffee expert who will explain why it can't be done.