1. Adult theatres were weird places but you could get a BJ in the dark sometimes.
2. It was hard to find someone to mop up the cum in the peep show booths that did not want union wages or combat pay.
3. Over the counter dildo sales died off in the '81 recession.
4. Glossy paper prices sky-rocketed.
5. VHS recorders were mechanical nightmares.
6. People bought computers and webcams were invented.

Most importantly, offline porn didn't adapt to the digital world.