In the final scene of one episode titled “Madrigal,” Walter White says that "There's no better reason than family.” Scott Meslow of The Atlantic singled that moment out as “a sentiment that could serve as an statement of purpose for [that episode]—and perhaps the entire series—which has seen virtually every character betray their morals and their best judgment in an attempt to protect the ones they love the most.”
The whole set-up for the series revolves around Walt’s desire to provide for his family after he eventually succumbs to cancer. This turns him to a life of crime, cooking crystal meth. When he tries to go back to an honest life because his wife leaves him over his criminal activity, he changes his mind because someone convinces him of his familial obligation to provide for his family, even when they’ve turned their backs to him.
Every relationship in the show seems to have some familial basis. Walt’s relationship with Jesse Pinkman is shaded by a surrogate father-son dynamic. (At one point, he even lies and claims Jesse is his nephew when he crosses paths with a figure from Jesse’s personal life)
Even the violent criminals in the show are defined by their familiar connections, often reflecting the familial model for criminal organizations seen in so many films and television shows going back to The Godfather. One pivotal moment even finds Walt surviving a near-death experience simply because his would-be executioner spares him out of familial duty, one that involve his own blood relatives and not Walt’s.
It’s not until the final episode when Walt concedes that familial obligation was at best an illusion or an excuse, that his criminal life was mainly spurred by his own self-interest, and it’s a realization that colors the show’s brutal end.