Part of it is definitely about Dick. The woman lying on Jason's left is the embodiment of everything Golden Boy ever held dear, and the fact that she not only gave a damn enough about him to not assume he was dirt in the sewers, but to also stand up to his big brother on Jason's behalf...well, that definitely plays a role in why Jason is here.
Part of it has to do with the little Speedy girl that turned down his offer. There's not a hero in the community (or a villain, really) that doesn't know how much Kyle Rayner means to Speedy's older brother, and if the fact that Kyle is curled around Jason's left side is causing the Arrows hurt, they damn well deserve it.
Part of it has to do with the Titans. The bastards couldn't be bothered to put up a memorial statue to him because apparently he wasn't good enough. Well, he's good enough to have gotten two of their best into his bed, isn't he?
Part of it is about Bruce. Nothing says "fuck you, old man," like giving the old "No Metas" policy a big middle finger. Considering how well Donna and Kyle like to flaunt their powers during sex, Jason can't deny that's exactly what he's doing.
What Jason won't admit is that late at night, when the darkness invades his dreams and summons old nightmares of digging out of his own grave, their relationship is also about having two strong arms pull him out of that darkness and remind him that he's no longer alone.