If they had a proper dining room, they probably would not have eaten on the billiard table. How come the mansion did not have a formal dining room?

I have a book of TV home floor plans, and the mansion DOES have a big formal dining room according to it. It is beside the "parlor" room, on the parlor wall that we don't see ~where the camera would be~ there are big double doors leading into the dining room, then it leads on back to the kitchen.

As to WHY they didn't use it, I dunno, I remember once I posed this same question. Ppl had theories like perhaps it was closed off and they just never bothered to look in there, OR perhaps they thought it was the slaughter room, I mean Granny would have had to skin and clean all those things she cooked SOMEWHERE, so perhaps she thought that's what it was for, of course the order of the day in the 60s would have be been allowed to show it in use lol