Fun they do anyway, but there are still a number of other applications in the design, the architecture, the product and company presentation, and in the scientific field. For example http://www.neuroteks.de/ at RWTH Aachen and Maastricht, they use 3D visualization of anatomical structures to generate clearer and more nuanced views in neuroscience.
In the field of medical-education and training are eg. operations in 3D video recorded to document detailed insights into operational processes.
Since there are visualization tools – from cave drawings, photography, film, video, internet – erotic content was one of the driving forces of new technologies. This is the 3D viewing without glasses just be with Eassee3D®.