I have a theory as to why we crave negativity.
Biologically, it helps (helped?) us survive.
By focusing on and remembering negative (read: dangerous) events, we are better able to avoid those same events for ourselves. Avoiding these experiences allows us to live to procreate. Ergo, those who were best at focusing on and remember the negative were the ones who were most successful in passing their genes to their offspring.
Today, many of us live in worlds in which we don't have to avoid the negative as a means of survival, but our brains and bodies are still wired to focus on and remember it.
Doing the same for positive experiences doesn't increase our chances of survival in the way that the negative does.
What do you think?
As for your questions, I am a happy and content person, although I often come across as cold, aloof, and weird. I do find those incessantly perky people to be kind of annoying and absolutely fake. I feel the same way about overly nice people though. I feel as if they can't possible really be that nice all the time. It's got to be exhausting and they've got to be lying.
I'm not entirely sure where that attitude comes from, except that the majority of the people I've known who were so nice to people on the surface were also quick to be mean and spiteful in private. I've heard it, I've seen it. That doesn't mean everyone is that way, but I definitely am more guarded around people who present as incredibly happy and nice than I am around people who present with more emotional variety.