Actually the procedure for seating used in Diners is highly variable. I traveled by the Silver Star and Meteor several times over the last several weeks. On different runs the procedure used were vastly different. ranging from "feel free to sit wherever you want" to " we must fill one table before starting a second table", and everything in between. So it is a mistake to generalize from one or two experiences. The only consistent thing that I found is the inconsistency between what different LSAs do. Apparently their training does not include training on a recommended procedure, or they simply choose to ignore whatever is taught.
So as a result there were occasions when I was able to chat with table mates, other occasion when I was seated with a lady who spoke 4 words of English, so not much to converse about with Yes, No, Water, and forget which was the fourth word (not the fault of the LSA). and another occasion when I was at my own table when given a choice, as that is my preference.
Actually do not under estimate how many people wish to sit by themselves if they can manage to do so. Everyone does not view the Dining Car experience as a way to enhance their social circle.
In general though a much larger proportion of Sleeper passengers are choosing to eat in their rooms than before the pandemic, at least on the Eastern trains with Traditional Dining too.