Ziggy is a better character when you know his story. I remember watching it live, and initially thought he was being portrayed as almost the dock's McNulty, a lovable fuckup who ultimately does the right thing. Instead he's just a fuckup who keeps getting in more and more over his head. He's the personification of the theme of the season, a generation who feels pressured to live up to the standards of the previous one, but without the support and infrastructure that the previous generation had. He would never have become his father, but he also didn't have the ability to see any other path for his life.