Are some people cynical without really having a good reason to be?

It seems like a lot of people, especially atheists, tend towards this attitude of cynical superiority, like "Everything sucks and anyone who thinks otherwise is an idiot." It's like in some way they take satisfaction from having "figured it out," and now they believe they have the right to look down on everyone who still thinks life isn't that bad.

I wonder, have these people really gone through life experiences or had certain revelations that cause them to conclude that "life sucks and then you die"? Or are they just emulating a behavior that they think marks them as enlightened and superior to all those who remain optimistic? I ask out of curiosity, because I used to be the latter, and have never yet heard of someone who fits the description of the former.