Why do people think aliens are real

I want to preface this by saying that I am not being condescending, I am simply trying to learn.

I was scrolling on my phone when I saw a video of someone saying that aliens are real.

I'm just curious - if you believe they exist can you explain why

Sure there is the fact that if they dont exist that means we're alone in the universe. But apart from that I haven't heard any other good reasons.