This being a quaint British novel, tea is a BIG FREAKING DEAL. It's served many times throughout the book. Mrs. Ali serves the Major tea in the first chapter. Then the Garden Club brings their own tea bags to the Major's house in Chapter 3. (How rude.) Next, Marjorie's tea "immediately began to give off a smell like wet laundry" (7.12). (Gross.) The Major later invites Mrs. Ali over for "just a cup of tea and a chat" (8.1)—but, of course, it's never just a cup of tea! He frets over the proper tea service to use as though his life depends on it.
And for the Major, it does. He is a very traditional man, and his life is tied to his customs. If he doesn't abide by customs, what does he have?
We're just gonna say it again, though. Teatime is the classic, quintessential, defining social custom for these village Brits. There's tons of etiquette involved, and everyone is watching you all the time to make sure you don't mess it up. So whenever these people sit down for a nice cuppa, you know that there are ten trillion things going on at once.