Another example from Europe that I've just seen: in Vienna's Shoenbrunn Palace[1], pretty much all grass in the gardens is off limit (but most grass in the public parks in the city is open). I suppose that makes sense because that garden is specifically made to look splendid, not for people to picnic on, and given the huge number of tourists coming all the time, allowing people to walk on that grass would quickly turn it into mud.

[1] https://www.schoenbrunn.at/