can’t say i know exactly which is the reason. but i will try.
i remember that when i was little, in my parents’ home all the tables they had were square. and it was the same in the homes of our relatives or friends.
square tables were by far the most common, in fact round tables were pretty rare. i don’t even remember seeing a round table at that time, at least not in the home of someone i knew.
so in my opinion, the traditional reason is the most likely. we were so used with square tables that we see them as being the regular, normal choice.
however, i can’t say things are 