What I was told was many of the weekly porn magazines that advertised local escorts and phone sex lines had connections with underworld printers, I imagine because of issues with advertising local hookers and strip clubs. Most disappeared in the early to mid-90s; Bill Margold's LA XPress is the only one I can even think that still exists in SoCal. Made sense to me when I heard it; who the hell else would operate and maintain those coin-operated machines?
Here (in San Diego) our printer for my old newspaper was bought out a few months ago and we couldn't find a single printer within a hundred miles willing to print it. We had an occasional porn picture
(Though I think issues like Jizzlam where angry muslims were threatening to kill us or our bomb whoever printed it) but it wasn't even anything totally porn-y. I was really shocked to hear just how conservative most the printers down here were.