Why are some airfields not on any sectional chart nor listed in the directory? I would have thought this was a safety issue.  Case in point - Hearst Castle Airfield.  This is located beneath William Randolph Hearst's Castle in California, located at  35°39'35.54"N  121°11'35.64"W.    

It is very obviously a well maintained runway, although private;  yet is simply does not exist if you were to believe the VFR sectionals.  It did appear in older sectionals, as discussed on the forgotten airfield site (http://www.airfields-freeman.com/CA/Airfields_CA_SanLuisObispo.htm#hearst2), but now not.  

If you look at skyvector (https://skyvector.com/?ll=35.658914169287556,-121.18517303105294&amp;chart=301&amp;zoom=1&amp;fpl=3539N12110W), the runway should be right smack under the crosshairs inthe center, where the map is marked "ranch".  But it's not there.  How can this be allowed by the FAA?  Even secret CIA runways are listed on sectionals.

I assume that the Hearst Castle administrators requested removal of the field from the map.  Isn't this a safety issue - in the event of an in-flight emergency, this would be a perfectly good field to land on, but being unmarked, there is no way to know it is there.  How can this be?
There are lots of airfields not listed on the charts or in the directory. For what its worth there is nothing that requires private airstrips to be listed. As mentioned in the comments sometimes its not worth the hassle. As you mention in the original question it is a nice gesture to list them for other pilots in an emergency. That is covered nicely in this question. They may not have listed it because they don't want people doing touch and go's there, or landing there and knocking the door of their house or they did not want to up-keep it etc. etc.