Erotic novels have been discreet for a while. It's also not been usual to have a laptop in public since the 90s. There are definitely pictures of people perusing porn on trains (visible in reflections).
Briefcases were also a thing as have been strip clubs since forever. Quick access to porn hasn't been a problem since the printing press was invented.
The difference is the volume and the lack of friction to access, not that these things weren't possible. Physically getting into a strip club or having to look the newsagent in the eye as you purchase a porn mag are much higher barriers to access than there are currently.
Briefcases were also a thing as have been strip clubs since forever. Quick access to porn hasn't been a problem since the printing press was invented.