The government hides the facts on UFOs because they think that populous can't handle the truth ; but more importantly ; they ; the government ; are arrogant.
The suggestion that any Government could sit on something so big for such a long time is somewhat ridiculous.
Certainly, Government's around the world have their secrets, but the thing with those is that they always inevitably get out. Someone always talks and the news spreads. The suggestion that any Government anywhere in the world has been sitting on something this huge, for such a long time and that it has yet to get out or have been leaked by any Government in all that time (remember, the suggestion is that subsequent Governments have sat on this secret for decades) is not realistic.
I mean, think about it, Governments leak like a sieve.
Even secretive regimes like in North Korea leak information constantly. To believe that any Government could sit on a secret that is that big, for decades, considering that in the West, for example, we have elections, new people coming in to replace the old, etc, people retiring, people being fired and in all that time, no one could actually confirm any of it, even today in the age of digital technology, where military secrets have been revealed in detail in leaks, that the existence of aliens visiting Earth could have been hidden... It is ridiculous to suggest such a thing.
Are there UFO's? Yes. There are a lot of things that we might see in the sky that we cannot explain, as such, they are unidentified flying objects. But there is not enough evidence to suggest that they are of alien origin. There is every evidence that they could be something else, something that is explainable and can easily be tested.