The Lazy Susan Is Neither Classic nor Chinese (2014) (smithsonianmag.com)

And one might think that if getting as much pressed duck as one desires were so important, one might choose to dine alone to one's heart's content.

You look around the table and see if anybody is currently serving themselves. If not you rotate a little ways. There is usually someone else who wants it turned. Since most of the meal is spent grazing and serving small amounts, the table really never stops turning.

There's a certain dance of courtesy when it comes to eating with a lazy susan that you eventually learn. Children were taught to yield the lazy susan to their elders first, otherwise they would be scolded by their guardian. This means hands off of the fun spinning table for kids. This is unless the guardian knows that the child (more so toddler/baby) is too young to understand table manners, and would otherwise cry from hunger. But in that case, it's the adult guardian that's spinning the table. And then there's the whole thing with who gets the last piece. Lots of small intricacies when it comes with family style meals, and spinning the table just makes it a little bit more interesting.

You don't know table manners/societal norms innately; it's a learned thing.

It’s impolite to have more than a few pieces of items in your bowl at any time.

Same.

These round tables are sometimes only in private rooms, with "regular" tables in the main restaurant space. That might explain why you've never seen one.

Usually the bigger ones which accommodate receptions and such would have them. Smaller ones, holes in the walls, etc, wouldn't nor would ones in modern, clean freeway-off-ramp strip malls, older ones may.

Because Wu’s table was never used for eating and is not the origin of the Lazy Susan dining table. The idea of using a rotating table to eat off of originated outside China.