I would speculate that the reason they don’t, is because NASA personnel know how far away the stars are. Furthermore, if they did acknowledge the possibility in any way, they would be totally unscientific as there is no evidence yet of extraterrestrial intelligent civilizations.
And it may well be there is no such thing as an interstellar spacefaring race anywhere! After all, the age of the Earth is a significant fraction of the age of the Universe, and in order for our Solar System to exist at all there must have been at least one complete generation of supergiant stars, and I think that in order to get the amount of interesting elements like uranium that we find on Earth there was probably another generation of star formation in between too. We may in fact, as improbable as it seems, be the first spacefaring life in the cosmos — we have exactly as much evidence for that as we do against it.