In The Pearl, John Steinbeck avoided giving the pearl buyers (as well as other characters) names and specific traits because those characters were intended to represent certain types of people and not to stand as individuals in their own right.
In The Pearl, why didn't John Steinbeck give the pearl buyers identifying names?
Before he wrote, Steinbeck always became completely familiar with his subject matter. This is not to say that Steinbeck lived with the Indians in and around La Paz before writing The Pearl, but the entire story is based on Steinbeck's actual observations. It was during Steinbeck's trip with marine biologist Ed Ricketts that he met these types of people and heard the legend of the great pearl.
In The Sea of Cortez, which recounts in detail the adventures and experiments along the Gulf of Mexico, Steinbeck describes the local Indians whom he met: They were totally illiterate, extremely poor, and lacking in any knowledge of the larger world, but nevertheless they possessed a sense of honesty, dignity, and humanity. They were, as Steinbeck points out, subjected to all sorts of primitive religious beliefs mixed with Christian teachings; they were superstitious, as are many uneducated natives. But beyond these limitations, these people inspired Steinbeck by their basic adherence to traditions, to courtesy, to integrity, and to humanity.
Yet they were constantly cheated by societal forces, such as the pearl buyers, and constantly humiliated by "civilized" forces, represented in The Pearl by the priest ("the Father" who tells them to keep in their social places and not to question those in power — such as the pearl buyers) and by the doctor. These observations aroused within Steinbeck a sense of indignation at the injustices that these simple people had to endure.
Thus, most of the characters in the novel are depicted not as full, three-dimensional characters, but as figures possessing certain traits that are representative of a large number of people. Like characters in a parable, they become symbolic of the function they play in the novel. For example, the pearl buyers are not distinguishable from each other; they represent, instead, a certain force in society that oppresses the Indian divers, and yet they are also victimized by forces above them. Steinbeck conveys the idea that these pearl buyers, if replaced by others, are no different from any other pearl buyers.