I am speculating, but there could be another reason for the current policy of who can view images, and it relates to bandwidth. Keith uses his own server and pays for the bandwidth we consume, and since all images uploaded to the SMC server must be downloaded each time they are viewed, this costs Keith. Restricting the viewing, and thus the downloading, reduces the bandwidth requirement. But I could be wrong.
This does not appear to be the case for images hosted externally, since the user's computer fetches the image from the external hosting site and there is no burden on the SMC server.
As a test, I am adding two images to this post. The first is from my external hosting site and the second is one I uploaded to the SMC server.
Everyone should be able to see this image of a car:
https://photos.smugmug.com/Cars-Plan...0Car%201-L.jpg
Only paying members should be able to see this image of a truck:
Attachment 409678