Information is a difficult thing to control. Two people can keep a secret if one of them is dead.
HAH! Gordon Cooper answered that canard better than anyone so far. He had first-hand involvement with things not of this world and his answer was ‘Well, someone has done a pretty good job of it so far.’ The poopooing factor is a big part of a negative normalcy bias. You’re doing it right here on this thread, maybe without even realizing it. Ridicule of those who have seen things you wouldn’t believe exists is a powerful tool ... with a herd.