Scout feels love in her home life with Atticus and Jem, and realizes that not everyone has this.
Scout is responding to the fact that Dill feels like he doesn’t belong anywhere, and has no close connection with his parents or home life. Scout feels like she belongs at home, with her brother and father. Dill feels disconnected to his mother and has no relationship with his father.
"Dill, you ain't telling me right- your folks couldn't do without you. They must be just mean to you. Tell you what to do about that-" (Ch. 14)
The reason Dill runs away from home is that he feels unloved. He doesn’t feel like his mother and her new husband need him. Scout realizes how luck she is to feel needed. Atticus always makes her feel loved and needed. Her brother Jem does as well, even though they argue sometimes. She feels a closeness to them both.
The reason Dill ran is the most telling reason of all. It is not because his mom and stepfather were abusive, but because he was lonely.
"That wasn't it, he- they just wasn't interested in me." (Ch. 14)
This is a realization to Scout, who tells Dill that sometimes it’s better for parents not to know everything you are doing, and that her father is not always there. He is not always physically present, but he is emotionally present in Scout’s life.
The relationship that Scout has with Atticus is a little different than most parents have with children, but it does not mean that he does not love his children. Atticus has his own way of showing affection.
Part of growing up is realizing that not everyone has what you have. Scout realizes that the relationship she has with Atticus is unique. Not all parents have such a close relationship with their children.