Why do aliens exist?

Answer 1

There are no aliens known to exist, just a bunch of anecdotes, and no matter how high you stack anecdotes, they never become evidence. We hope there is other life out there, and we consider it likely. But someone has to be the first form of intelligent life in the universe, and there is no evidence that it isn't us. Whoever it was would look up at the vast universe and think it was so large it must full of life. And they'd be wrong.

For a while people thought they'd found fossil life in a Mars meteor. But since then it has been pretty well established that the "fossils" were just tiny lumps of mineral, too small to have ever held a working supply of anything resembling DNA.

if you mean the extraterrestrial type(also means aliens), it is because the universe is just so huge that earth just can't be the only place where life has arisen. but the vastness of space also means that it is ridiculous that UFOs, etc, are visiting earth. they are probably sitting on their own planet, asking themselves the same questions, far, far away.

You could ask the same question about humans. why do we exist? What is our purpose? (if it's to get drunk and yell at each other, we passed with flying colors.)

There is no scientific reason to assume there are aliens. I'd like there to be, at least I think I do. But someone somewhere has to be the first form of intelligent life in the universe, and there is no evidence that we aren't it.