Before the days of Usenet and freely distributed pornography, even before the days of VCR's and videocassette pornos, before anyone would dare mass distribution of a pornographic magazine, there were pornographic picture shows.
Popular in the 1920's, when picture shows in general were still quite new, pornographic picture shows were something new and tantalizing to the male population. These shows were so popular that they made up approximately half of all the pictures shows produced during that time period. Never before had anybody seen a moving, naked woman except in real life (and some of these men hadn't even experienced that).