I am not sure this is the complete explanation.
On Earth we do not see stars because of light scattering (Rayleight and Mie) [0].
In the outer space there is no scattering and the light from each star represents a tiny point in the picture, but this point is bright. After all it comes from a sun. But the original image [1] has a dark background as well.
Maybe it is due to the fact that jpeg compression losses small artifacts or something else.
On some pictures it is possible to see tiny white points such as in [2]
We see stars during solar eclipses, so it is the scattering of the light of the sun that obscures them. It really _is_ the exposure issue, since the surface brightness of the Earth is that of full daylight and so full daytime exposures were needed. Stars will never show up unless longer exposures are used.
Here is an over exposed photo of Earth by Apollo 16 from the lunar surface, with stars visible:
Maybe it is due to the fact that jpeg compression losses small artifacts or something else.
On some pictures it is possible to see tiny white points such as in [2]
[0] https://en.wikipedia.org/wiki/Diffuse_sky_radiation
[1] https://www.hq.nasa.gov/office/pao/History/alsj/a410/AS8-14-...
[2] https://www.hq.nasa.gov/office/pao/History/alsj/a410/AS8-15-...
(some non important edits, including changing link 2 which was a thumb view)