Why aren't AMA certified radio-control club sites shown on aeronautical charts? All this drone business wound up affecting us R/C fliers that fly only at local verified club sites. I wrote (told) the FAA that our local AMA R/C flying fields are constantly having "our" flight areas intruded on by full-scale aircraft that unknowingly fly over our field.

Why are permanent R/C airfields not shown on aeronautical charts?

In response to comments: 


We are not near an airport.  
We take note when overflown by 2500' or less
Drones with FPV can easily stay under 400' AGL as suggested by the FAA but they will very likely not be aware of the location of manned aircraft
Other RC aircraft have no way of knowing where the 400' limit is and can easily go much higher, and manned aircraft would not be aware of this
Model aircraft flying areas may be registered with a group such as AMA but there is no requirement to register these areas with the FAA. The current FAA rules expect RC pilots to stay out of airspace in use by manned aircraft, or give way to manned aircraft at all times.
It would require a lot of extra work for the FAA to register every AMA field and mark them all on charts or to enforce restricted areas around them. Also, model aircraft are not limited to AMA fields. This seems to be a reasonable compromise: the FAA lets you use the airspace as long as coordinate with nearby airports and avoid all manned aircraft.
The FAA has provided guidelines for model aircraft flying an an Advisory Circular (AC) as of January 2016:

Model aircraft operators should follow best practices including limiting operations to 400 feet above ground level (AGL).
The aircraft operates in a manner that does not interfere with, and gives way to, any manned aircraft

If you stay under 400 feet as the FAA suggests, you will not be interfering with manned aircraft, which should not fly any lower than 500 feet.
If you choose to fly above 400 feet, it is your responsibility to avoid manned aircraft. You can see them but they probably can't see your model aircraft. Stay aware of your surroundings, use a spotter if you have to.
Remember that the airspace belongs to manned aircraft, and you are only allowed to use it if you don't interfere with them.
See related question: Where is RC aircraft flying allowed in the US?