People learn by watching or observing. Its a basic part of the scientific process. You want to see people having sex because it arouses you so you can relieve your own personal sexual tensions. Thanks to these fantastic physical motion actors, you can learn new ways of sexual pleasure that you had not thought about before. Maybe when we’re all gone, aliens will finally figure out why all pizza has a hole at the center. They will find Fred Thompson’s laptop under the rubble created by a thousand earthquakes after eons of human inexistence and the hole in the pizza will be explained away.