It isn't bizarre that rules and practice vary widely in different cultural contexts. Even your claim is caveated as "most of EU," recognizing that it might not be the same in all places.

In many places in the US, there is a culture of legibility, whereby informational affordances are relevantly and generously provisioned. This allows for more certainty for both facility users and rule enforcers. On the flip side, there are a lot of signs all over the place.

Reviewing the thread, the context is newly enforcing something that might not be illegal in all jurisdictions. Citing different contexts where signage is not always used doesn't change the fact that the discussion focuses on change in common practice in a specific context. In fact, I observe plenty of signage for fire hydrants and driveways in places where people commonly make parking errors.

The question still stands. How do you ensure you detect changes rules of the road in order to maintain your privilege?

  >>>>>>> Where I live, many people park at intersections right up to the curb
  >>>>>> This is now illegal in some states
  >>>>> It's illegal in California but in San Francisco official policy is to not enforce this law.
  >>>>> If there's no red paint on the curb, they won't ticket you.
  >>>> It was ridiculous that they were originally proposing ticketing people without there being signage that it was illegal to park there.
  >>> Why? Having a driver's license is a privilege that requires you to study and know the rules of the road.
  >> Do you have an rss feed of road rules piped into Anki cards or what?
  > No, I don't; there are plenty of places you can't legally park that do not have painted curbs or "No Parking" signage.