and the principal male and felmale quests were usually the only people at a formal Georgian dinner who had designatd places at the dinner table.

Do look at this from Maggie Lane's book Jane Austen and Food which explains why Mr Collins feels so honoured to be carving at the opposite end of the table to Lady Catherine.

As today on formal occasions, host and hostess sat at the head and foot
of the table.

If the master of the house was absent, a strict hierarchy
obtained as to his substitute. In Sir Thomas Bertram's absence, Tom
takes his place, but when Tom too departs for the races, Mary Crawford
knows for a certainty that Edmund will be at the head of the table.

In this respect, though not in the courtesies attached to the position, Mr
Woodhouse has abdicated his place as host; when Emma plans her
dinner party she assumes that Mr Knightley will take his seat at the other
end of the table from herself. The arrival of Mr John Knightley in the
house forces a change, much against Emma's will, for 'she thought it a
sad exchange for herself, to have him with his grave looks and reluctant
conversation opposed to her instead of his brother'. (E, 292) Her wishes
in this respect are foreshadowing of their partnership in marriage -
another clue to her feelings that she fails to notice. Etiquette dictates the
exchange not in this case because John is the elder, for he is not, but
because he is the house guest and related to the family by marriage,
whereas his brother is merely (at this date) an old neighbour and friend.

The person who gains most in elevation from the lack of a master of
the house is Mr Collins at Rosings. 'He took his seat at the bottom of the
table, by her ladyship's desire, and looked as if he felt that life could
furnish nothing greater.' (P & P, 163)
Page 40.