I notice in TV shows, such as the Sopranos and Law& Order that when people buy a few cups of coffee (paper or styrofoam cups), they are often carrying them in paper bags. Is this common? Why? Where I'm from fast food and coffee chains use cardboard drink trays. I'm sure paper bags are eco conscious, but wouldn't they be unstable? Especially if liquid is spilled on them. thanks!

Why do people use paper bags for holding takeout coffee cups?