It makes no sense for us to be alone in the universe, as the universe is infinite. Our definition of our little section of infinity, as created by the "big bang", is fine, but our definition of ourselves as the only sentient life form that is advanced enough to put space junk around our planet and to send a few probes deeper into our part of space is one that is, at best, taken on faith.
Since the top scientists once believed that the world was flat and that the sun revolved around it, we are exponentially farther along in our ability to make up and to confirm theory, then to get people to believe in it. It is simply equally as legitimate to believe, based on partial evidence, that sentient beings travel here, may have put us here, and may be among us to an extent that would be shocking to know: as our ancestors who mix , match and reproduce with us as easily as we mix, match and reproduce with each other.
It would be a revelation to know that mutations that have occurred throughout the history of mankind were not accidental or natural, but were the result of God's tweaking of our genome. Many mutations and evolutionary developments (except for humans walking upright, a development that has not proved to be an efficient way to get around), have been surmised to be responses to specific external threats, toxins, or diseases.
The sickle cell trait, which is not exclusive to people with African ancestry, famously provides some form of protection against the Malarial parasitic process. The human head has gotten to be too large in relation to the size of the birth canal and pelvic region. The post birth, neonatal stage of infancy is a very tenuous adjustment and development period in the life of an infant who would seem to be better off staying in the womb for four more weeks if it were not for that huge head.
But as far as the "Men In Black", the "Black Helicopters" and the vast lists of conspiracies, the only time when we see such things is when individuals get too close to ultra top secret facilities and make themselves obvious enough to draw the attention of the advanced and extraordinary security that top secret facilities are known for!
The human entity is known for it's inability to keep anything completely secret. We are, as a whole, far more resourceful in finding out what people do not want us to know than ever in the history of mankind. But revelation and apocalypse are events that overwhelm the human capacity to discover secrets.
The true definition of apocalypse is that revelations that are given only to the chosen. And yes, there are hidden truths of an apocalyptic nature concerning our possible interactions with living entities from other parts of the extended and infinite universe. Our governments have many reasons for the apocalyptic treatment of such information, and for aggressively enforcing the secrecy.
Proof aside, it is entirely acceptable and logical to believe that, not only are there other life forms in the infinite universe, that they have been, are, and will be interacting with us in some form or another. It is entirely logical and reasonable to assume that our governments have been interacting with such life forms.
It is even more logical and reasonable to let society be in the dark, given Human behavioral and social history when it comes to revealing the truth of matters that could challenge all religious dogma and societal control, could cause dramatic acting out, based on religious, social, and political hysteria, and could result in catastrophic failures to maintain order in the world.