And more concretely, you're determining someone's values before offending them. Through small talk you might discover they're more conservative. Maybe they're hippies at heart. Maybe they hate dark humor, maybe they love it.
If you know those things, you can choose which serious conversations you'd like to have and which you'd better avoid. Plus the process of sniffing each other out means there's more baseline trust going in.
From that perspective lots of communication make (more) sense. The signal always carries emotions in a way. Bandwidth is limited and parts are reserved. Some can control more of it for logic and argument. Speech seems to be trust and relationship building.
edit: Typo
I mean Ryan gosling face has 0 bits of information in blade runner and yet we know he's pretty sad and emo.
You might want to revise that as "no unpleasant surprises and minimal surprises in general".
People will always surprise you, but we prefer pleasant surprises.
If somebody gets into discussing the current state of a low-pressure weather system, or talk about the finer points of the difference between the theatrical release version and the director's cut of a recent movie, or compare batting averages across decades, etc — it's not small talk any more, it's geeking out :)
-- David Foster Wallace