Why is this question about https://skeptics.stackexchange.com/questions/776/life-in-other-planets closed as off topic? Subjective & argumentative sure, but why off topic? Where would it be on topic?
Questions are off-topic if they're not skepticism of something. This question is skepticism of... who or what exactly? What did you hear that made you write the question?
To my knowledge, it's skepticism of nothing.
One of the best advice I could give to any asker is that, if you want to have the best answers possible, quote the claim you heard. Don't just try to summarize it. If you quote the claim and attribute it to whomever said it, we'll have a better idea of what's being discussed than if you write to lines about it.
I don't know whether it is a widespread belief, that we are the only planet with life, but I can imagine so.
Mankind had difficulties to accept, that the earth isn't the center of the world (Kepler?), that we are a kind of apes (Darwin) and ruled by drives (Freud). Today, it is partly accepted, at least that the center of our universe is the sun. The big, big count of other universes isn't known to a majority, I guess, but I can only guess.
Very much people get ignorant after leaving the school, and tend to simple viewpoints. Life in far away universes is a nice movie plot, but so are zombies.
I agree, that the assumption is a bit weak. I would argue, that the invention of god is a hint, that people are egocentric, and that it violates their ego if they aren't the
the pride of creation.
I observed people, searching for evidence, that human beings differ fundamentally in some respect from animals, and as soon as an counter example was found in the fauna, the fundamental aspect jumped to another distinction, but the big theory was held up: We differ fundamentally from the beast!
From the usage of tools, to laughing, to speak, to sorrow, to building tools with tools, to building culture and to abstract thinking. Often people aren't up to date, and get confused when confronted with recent observations.
In my opinion, skepticism isn't so much the knowledge of recent studies, but the ability to reason with what you have, with logical thinking and the willingness to scrutinize your own viewpoint.
I thought that a lot of people are religious, and that aliens would look somehow alien to their believes: Noah didn't take a pair of aliens on deck - to begin with.
But I googled and found this study about believes, that aliens are already in between us: 20% believe it worldwide. (only a part of the world was asked). But this is very much, compared with the idea, that aliens just exist, had existed or will exist, but far away.
So the number of believers in extraterrestrial life seems huge, so
widely believed seems indeed exaggerated.