Why obviously, to prepare us for the upcoming reveal of our new alien ‘friends’ who will tell us how they’re so eager to help us cure cancer and eradicate poverty and all this other wonderful stuff, just as soon as we turn in all our scary weapons and embrace the socialist hive mind.
:P
(Is it just me or does Zuck look like an alien breeding experiment?)
There is a great deal of lore regarding those things, and physical evidence does exist. One interesting story is Train hits UFO
Mockery is a frequent tool used on folks who have witnessed unusual sightings or even on those who would prefer to have a serious conversation. Instead of mocking people, do some reading. There is substance to UFO stories, certainly thousands of credible witnesses.