What about airfields with noise-abatement procedures?
Put it in the AIP or on the website, or flight guide?
Not everyone buys flight guides, not all airfields are in the AIP
What about airfields like Duxford who may have regular display practice taking place?
NOTAM it, tell people over the radio, put it on the website...
Again there is nothing to guarantee that people will read the websites, I can't remember the last time I looked at the website of an airfield I visited. NOTAM? PPR is a lot simpler to administer. Telling people over the radio? PPR would save inconvenience to everyone including the visitor.
What about airfields that are not attended all the time?
Who cares?
Who cares? maybe the person collecting the landing fee? or wanting the aircraft parked in the right location, any number of reasons.