In the analog world, we capture patient records and then transfer the information to an articulator with mounted models. The goal is to simulate patient movement so that we can ensure that teeth do not hit and slide when a person is eating and talking. The gentle (or not so gentle) wear from hit and slides are the cause of many restorations.
One of the most important things to understand in the Digital Design World is that what you see on the screen is not necessarily accurate. How many times have you designed a smile case only to produce it and find the centrals are too short, too long, or the midline is canted.