A background character walking across the street doesn't need any character development.
Thats a plot hook, not necessarily a promise.
One reason why I asked this question is because of how I am regarding to Harvey Girls Forever! (formally called Harvey Street Kids during its first Season). The show ended two year ago, yet with how it lasted for four Seasons, it ended with some unresolved stuff. Why can't the show last longer or at least continue with another series just so that it would start to later focus on character development?