So you're saying that no lay person can share interesting facts during casual conversation? You must be an expert on something to casually talk about it at lunch? Nonsense. This is one of the sillier things I've ever read on HN.
It's not a matter of arrogance, pseudo-intellectualism or anything else. It's a matter of wanting to share interesting things one knows.
The phrase "I explained about longitude" paints a very different picture in my head to "I told my friends about this great book about longitude", but maybe that's just me.