Unless to increase the stars and moon to unrealistic high brightness, stars are super faint. You need to use long exposure to see them. Usually when you have other lights in your scene, the auto exposure regulates the exposure down.
This is also observable on real photography, like e.g. the images from the Apollo astronauts where you do not see stars at all due to the bright lunar surface
OK, got it.... thanks,
but anyway also for this kind of situation (nightly scene, subtle blue sky illumination, soft reflections) I think we really would benefit from a option to be able to optional define separate skyboxes for lightning, reflection and background, see here:
about realism in general: realism is most often a good starting point but most of the time when doing architectural visualization we have to be able to "alter" the realism here and there... a good example is the brightness of the inside of a house when viewed from the outside, usually in real live they would appear pretty dark, so we often have "make" them more bright , or over bright ("burned out") windows / outer environments when doing indoor renderings...
One of the reasons I am so fascinated by enscape is its ability to create "nice" looking pictures with a relatively even bright indoor appearance which is what we are aiming for in 90 % of e.g. indoor pictures. That is not realistic but it creates good pictures without the usual effort (fill lights, reflective panels etc.)