I make no truth claims about UFO sightings. Simply because I don't have a particular experience, doesn't mean other people haven't. But since UFO sightings are not a common experience they have limited utility as cultural stories. How does the story change how I should behave? On an individual level they are interesting because it carries information about the teller.

Kind of like me telling someone about the time I hiked to the bottom of the grand canyon. It has no cultural significance but it does have interpersonal significance.

Though I will admit seeing a UFO is a much more interesting story.