Remember there's no (or so little as to not matter) scattering of light in space. Almost all the light you see comes out from the sun and reflects off the three objects in the photo. Earth, Moon, spacecraft. The spacecraft (obviously) is closest and very reflective, so it's going to be the biggest light source in the image. That bright source will determine what exposure is required to be able to pick out the detail they can. A longer exposure would wash out the image and a shorter one wouldn't pick up enough light to see the Earth and Moon in any detail.

If the camera was pointed out away from everything and a photo taken with the correct settings, you would see stars. For example this photograph taken from the ISS.