Of course we know cups joseph, but: 1. cups are more expensive than a plastic bag. 2. this technique is mostly used in schools (with kids)and they're always runing and playing and a cup spills, a bag doesn't. 3. It is also used for example when your mom sends you to the store for a coke, and there goes the kid runing, and they give the kid the coke in a bag closed with a knot, instead a cup that spills.
1. cups are more expensive than a plastic bag.
2. this technique is mostly used in schools (with kids)and they're always runing and playing and a cup spills, a bag doesn't.
3. It is also used for example when your mom sends you to the store for a coke, and there goes the kid runing, and they give the kid the coke in a bag closed with a knot, instead a cup that spills.