Because their locations are or were undisclosed, and obviously not even everyone here has heard of them. They exist.
Edited in reply They are explicitly said to exist in Hollywood propaganda film Zero Dark Thirty (2013). No, this is not proof, although it is evidence. If the establishment wants us to believe they exist, is that not troubling enough?
Edited in reply They are explicitly said to exist in Hollywood propaganda film Zero Dark Thirty (2013). No, this is not proof, although it is evidence. If the establishment wants us to believe they exist, is that not troubling enough?