Like a uncle of mine used to say when the subject of alien beings in space ships came up.
"Where are they of they have been here all of this time?"
Well there is the theory that they have already been here, got what they needed, wanted and left. To boring, not $$$ feasible, off the main trade routes who knows.
“Non religious people always criticize the faithful for believing without proof. These same folks will except the existence of extraterrestrial beings without proof.”
I guess eyewitness accounts of the ministry of Jesus are not proof enough?