An open house lead is a person who attended an open house and provided enough contact information for the agent to reach them afterward. Most are early-stage: still looking, often unrepresented, and worth a same-day first touch.
These leads convert at a low but real rate over the following months, and the deciding factor is follow-up. A lead you contact the same day and keep nurturing converts far more often than one you meant to call and never did.
Treating every sign-in as one undifferentiated list is what wastes them. A visitor who is unrepresented, pre-approved, and looking to move within a few months deserves a call before you leave the property. A neighbour comparing finishes, or a buyer whose agent is parking the car, belongs in a slower sequence. The sorting has to happen while the context is still fresh, because by Monday every row looks the same.