Why might people prefer not to move beyond small talk?

I’ve seen people here say they hate small talk. I’ve seen it a lot. It got me to thinking about the role of small talk—which, I believe, is a kind of “grooming” behavior.

However, to go beyond small talk, you have to start talking about things you care about. This could be bad if you don’t want to reveal things to the person you’re talking to.

I’m sure there are lot’s of things people are justified in hiding in order to save themselves from being judged: sexuality, religion, politics, mental health conditions, etc. Probably people also just don’t want to get into a serious discussion. Maybe they’re not up for it. Maybe they have nothing else to talk about.

What do you think? Is it a preference or a lack of ability? What explains the prevalence of non-serious communications?