Hi and welcome! The reason is simple: the type of lens used for surface photography (not including the closeup, stereo and 500mm lens) as follows:

Hassleblad 70mm
Superwide angle camera
38mm lens

Hasselblad 70mm
EL Data Camera
60mm lens

Both lens types are considered "wide" angle lenses (well, the 60mm is more like a standard lens). Primarily used as landscape photography lenses. Things that are far away will appear smaller than in reality. I took a photo while in Warsaw last year of the "Russian Palace of Arts" over which a beautiful and _large_ moon hung. When I looked at the photo at home, it was no where near as spectacular as what I saw with my eyes.

Furthermore, if you have the Apollo TV dvds, find the section where Ed Fendell points the LRV camera at the earth. You will definitely see a large and spectacular earth in the shot, and also a good example of what different lens specs (in this acse a zoom lens) will do to an image.

BTW I am working from rusty memory of photgraphic principles here, so if anyone could check the maths, that would be most welcome.