Throwing pots on a wheel is a common way to shape clay. It provides the artist with a round object. The spinning of the clay makes it easy to form plates, cups and pots. All of these objects are traditionally shaped into a round form.
There are other ways to shape clay into useful objects. Sculpting clay by hand is one way. Creating forms in this manner can take longer, but there is no limit to the shapes that can be made by using this method. Mixing clay into a water suspension and injecting it into molds is another way to shape clay. This is a method employed by manufacturers who need many clay items of the same shape and size. A mold can be used many times to make identical objects.