This not only makes butter (which you can flavor – cinnamon, dill, garlic, blue cheese, and etc. just as you would with bought butter, but it also nets you commercial grade fresh buttermilk.
By making your own, you can ensure quality. For instance I usually only cook with sea salt, so I could make a high grade butter that way. Or I could use different types of cream or even blend in high grades of olive oil. Endless possibilities.