Playing billiards and having tons and tons of books. I also forgot to add chess in particular.
People can possess enormous collections of books, and do, but I really bet them that they don’t pick up to read a single one. Only to sometimes bring up certain lines to win online and pointless arguments over.
Billiards is usually a bar/pub kind of game, but some others seem to associate it with intelligence. You don’t need to be intelligent to play billiards.
Chess is self-explanatory. Lots of people throw around the line of “people are playing checkers while X plays chess” and other similarities. I think people look way too into chess as being a measurement of intelligence.
How many people actually collect books for show? That seems uncommon and it should usually be fairly easy to tell for people who are somewhat well-read.
The thing with chess is that it’s not fun if you aren’t any good at it, and the difference between people who are somewhat good and those who aren’t is pretty big. You can get there with pure perseverance (same with most other things that gets listed here, probably), but most people tend to pick hobbies that they don’t have a hard time with.
Collecting books for show was such a thing it was used as a literary device in the Great Gatsby.
See back then, books were mass produced via multiple stitched together folded booklets, much as they are now, but they didn’t have the cutting technology to trim the edges.
So readers would have their own “book knife” or “paper knife” and cut the folded pages apart to be able to read them (resulting in a “deckled edge” which is now simulated these days in some printings.)
So when Gatsby’s library is carefully inspected:
"A stout, middle-aged man, with enormous owl-eyed spectacles, was sitting somewhat drunk on the edge of a great table, staring with unsteady concentration at the shelves of books. As we entered he wheeled excitedly around and examined Jordan from head to foot.
“What do you think?” he demanded impetuously.
"About what?’
He waved his hand toward the book-shelves.
"About that. As a matter of fact you needn’t bother to ascertain. I ascertained. They’re real.
“The books?”
He nodded.
“Absolutely real - have pages and everything. I thought they’d be a nice durable cardboard. Matter of face, they’re absolutely real. Pages and - Here! Lemme show you.”
Taking our scepticism for granted, he rushed to the book-cases and returned with Volume One of the Stoddard Lectures.
“See!” he cried triumphantly. “It’s a bona-fide piece of printed matter. It fooled me. This fella’s a regular Belasco. It’s a triumph. What thoroughness! What realism! Knew when to stop, too - didn’t cut the pages. But what do you want? What do you expect?”
He snatched the book from me and replaced it hastily on its shelf, muttering that if one brick was removed the whole library was liable to collapse."
The Great Gatsby is 100 years old. I’d assume that books were still more expensive back then relative to people’s incomes, and they were also the only way to access that content while today you have e-books, PDFs, YouTube-videos or even websites, which are often available for free (not necessarily legally).
On top of that, many literary devices are unrealistic or exaggerated.