Function to 'deactivate' images. Nude models have been prevalent since man first created art. To the Greeks and the ancient Romans, to Renaissance artists and for modern art studies, the nude model has been essential. Even the less artistic uses of nude modeling have some value, though mostly monetary. After all, the porn industry is a thriving business in Southern California and has more recently grown into a colossal industry.
Easy examples are nude women in magazines, movies, and on the Internet.
The uses of nude models are definitely out there and probably always will be. The same for girlfriends. For every boy there is, yes, a girl to match,, most of the time. And without girlfriends there would be less room for heterosexual monogamy, except, of course for marriage. These are two subjects that should have a permanent, dark and definitive line between them.