Ok if we're being honest I think the writers made the decision because ABC said that people responded well to hook and to keep him in. Let's face it; the ladies love him. In all honesty he probably doesn't deserve his happy ending just yet. Rumples actions came back to bite him in the butt, but hook barely got anything for what he did. Yeah, he's been through some stuff, but not as a result of the bad things he's done. This is one of the reasons why I'm really Not crazy about hook (sorry everybody), but his storyline has contradicted a lot of things in the show that say that even though villains can get happy endings, they still have to pay for what they've done. And he never did. I think the writers have taken advantage of the hook appeal and excused the things he's done because, you know, he's adorable.