>While this is true, there are billions of convenient examples everybody knows.
Well, in those days they had a billion less examples than we have today - or at least tens of thousands of common today product categories and things not yet existing.
But they also used weaponry (Zeno on infinite division), chariots (Plato on soul), pots (Plato on art), caves (Plato on reality), dice (Heraclitus on chance), and many other things.
Plus, famous examples tend to be re-invoked (same how computer vision students re-used Lena).
Both are fair points. Still, a table - or chair - is/was one of thousands of options to choose. So you might be right that good examples tend to be reproduced. Question remains why it would be a good example to begin with.
Personally I think at some point such choice became baked in into the concept of physical existence because people think in pictures and physical existence in itself is such an abstract thing. The choice of furniture however is kind of hilarious.
I will bite. How do these multi-thousand-year furniture lobbyists continue to conspire to successfully frame our contemporary ideas toward their agenda?
Some evidence that I'm not joking, two more or less prominent examples...
From Roger Penrose's "The road to reality", chapter 1.3 "Is Plato's mathematical world ‘real’?":
"I am aware that there will still be many readers who find difficulty with assigning any kind of actual existence to mathematical structures. Let me make the request of such readers that they merely broaden their notion of what the term ‘existence’ can mean to them. The mathematical forms of Plato’s world clearly do not have the same kind of existence as do ordinary physical objects such as tables and chairs. They do not have spatial locations; nor do they exist in time."
"How" you ask.. I think we need to trace back when philosophers started to hit on that meme. I think the "multi-thousand-year furniture lobbyists" started to jump on the bandwagon from there and things co-evolved after that. I am determined to solve that humandkind-old mystery.
I'm not convinced. (I don't thing so.)