They can hardly run around sticking everyone for having what everybody can have easily and what is not easily visible unless too many people start collaborating and reporting each other.
Enforcement will never be completely universal and the more "free" the society is in general the harder it would be to enforce it via draconian means.
So the dry laws in the US and in other western (primarily Nordic) countries isn't that great of an example as these were still mainly liberal democracies despite the restrictions.
The similar laws in more authoritarian regimes would work quite differently.
And unfortunately we have too many modern examples of how effective governments can be at suppressing various behaviors and or ideas.