To paraphrase Tolstoy, happiness is usually pretty boring. That's why most novelists don't spend much time on it. It's way more interesting when characters are mooning around and miserable, which also explains the popularity of emo music. But it turns out, most of the folks in Cannery Row are actually happy. Is this why Cannery Row never became one of Steinbeck's heavy hitters?
Being broke and hungry doesn't get Mack down, but feeling rejected by the rest of Cannery Row really ruins his mood. In this world, relationships with other people are more important than having enough to eat.
Doc is the only unhappy character in Cannery Row.