The Pearl has a simplified plot structure that reinforces and underscores the ethical message against greed that the novel is trying to convey.
Each chapter has one main incident, which then has an impact. For example, in chapter 1, a scorpion stings the baby Coyotito, leaving his poor parents desperate for money for medical care. In chapter 2, the main incident is the finding of the pearl. This has the impact putting Kino at odds with the rest of the villagers.
The novel is structured more as parable or story meant not so much to be realistic as to teach a lesson. In real life, a poor family would not likely find a priceless pearl the moment they need financial help. The pearl is not so much a realistic find as it is a symbol of the temptation of wealth and greed. Likewise, Kino is a simplified everyman figure, representing any poor person who has to struggle internally with the temptation of more wealth than he has imagined. The incidents in the novel are stark, from the finding of the pearl to Kino finally renouncing it and throwing it back into the sea.
The plain language, with its declarative statements, also supports the simple moral of the tale. For instance, we learn the following:
All manner of people grew interested in Kino—people with things to sell and people with favors to ask. Kino had found the Pearl of the World.
This leaves us with no question or ambiguity as to why people are suddenly interested in a simple fisherman like Kino.
Symbols are simplified, too. For example, the evil of the scorpion's poison that infects Coyotito becomes the poison of greed that infects the town:
The poison sacs of the town began to manufacture venom, and the town swelled and puffed with the pressure of it.
One of the reasons this novel is still read is the way its parable-like structure reinforces and makes clear the story's central message.