That's probably true for authors as well (not that I am one).
I suspect these trades are artefacts of that way of thinking. Some people have a frequent flow of ideas they are compelled to capture in one way or another.
Why do comedians feel the need to tell us how hard their life is all the time?
Because they want to talk about things from their life (which is because, among other reasons, having personal experience with the things they're talking about is rather helpful), and if they were saying how great their life was, that might evoke resentment. It also seems possible that the space of "funny things you can say about how something sucks" is bigger than the space of "funny things you can say about how something is good".