In "Cathedral," why does the narrator continually refer to Robert as the "blind man," rather than by name?
It may be a mistake to attach too much significance to the fact that the narrator keeps referring to Robert as "the blind man." When an author gives a character a particular identifying habit or physical trait, he has to keep reminding the reader of it or the reader is likely to forget it. Such an identifying mark is sometimes called a "shtick." It is of the utmost importance that the reader visualize Robert as blind, but the name Robert is of no great importance. This is largely a matter of narrative technique.
In The Catcher in the Rye, for example, Salinger keeps reminding the reader that Holden Caulfield is wearing a red hunting hat. This helps the reader visualize the hero, and it also serves to characterize him as still a kid trying to be a grown-up, as well as possibly to characterize him as someone who is "hunting" for something. The hunting cap is a "shtick." There is probably no better word to describe these literary devices.
You will note that there are other things about Robert which the author keeps repeating. One is the fact that the blind man has a beard. This is of no importance to the plot, but it helps the reader to visualize Robert. Here are a few examples:
"I have winter in my beard now."
He lifted his beard and he let it fall.
As he listened to me, he was running his fingers through his beard.
There are several other places where Robert handles his beard. The narrator is telling about something that happened in the past. He would not really remember the various times that Robert touched his beard, but Carver risked the threat to his verisimilitude because as a good fiction writer he knew it was important to maintain some impression of the blind man in the reader's mind.
Carver also gives the blind man at least one identifying speech habit. He keeps calling the narrator "Bub." There is no great significance to this; it just helps to characterize Robert and helps the reader remember him.
"Bub, I'm a Scotch man myself," he said fast enough in this big voice.
"Right," I said. Bub! "Sure you are. I knew it."
You will find many more of these "Bubs" throughout the story.
A good example of how an author will use speech pecularities to characterize and maintain an impression of a character can be found in James Thurber's often-anthologized story "The Catbird Seat." Ulgine Barrows, Mr. Martin's nemisis, keeps using using expressions she picks up from listening to baseball games on her radio.
She had, for almost two years now, baited him. In the halls, in the elevator, even in his own office, into which she romped now and then like a circus horse, she was constantly shouting these silly questions at him. "Are you lifting the oxcart out of the ditch? Are you tearing up the pea patch? Are you hollerinig down the rain barrel? Are you scraping around the bottom of the pickle barrel? Are you sitting in the catbird seat?"
One of Martin's assistants explains:
Red Barber announces the Dodger games over the radio and he uses these expressions--picked them up down South. . . . "Tearing up the pea patch" meant going on a rampage; "sitting in the catbird seat" meant sitting pretty.
These zany repetitions of annoying nonsensical questions are part of Ulgine Barrows' "shtick."