A liquid does not keep its shape. It needs a container if it is not to spill over the ground. Gravity helps to keep it at the bottom of the container. Water has to be kept in a pond or tank. If it is the container has a hole, the water will leak out.
Milk is delivered in cartons and bottles, otherwise it would leak all over our refrigerators. Washing up liquid is stored in special bottles that you squeeze to help the liquid out at the top.