why does steinbeck mention that george and lennie had problems in weed but then not develop the story

The problems they had in weed foreshadow what is to come in the story. The event frames the obstacles George faces when Lennie gets in trouble, especially when he has contact with young lonely women at a ranch. George liking soft things combined with the fact that Lennie is a child in a man's body makes even the most innocuous encounter with a girl potentially tragic. The reader keeps the episode in Weed at the back of their mind so when the climax coms, there is context for it.