A lil something about Sam and Dean and Jack and humanity
I don’t want to be that person all the time, but I’m not sure we have really pointed out the fact that Sam “This is a human!” (line from 13x02) Winchester is extremely focused on the non-human part of Jack: his powers, the issue of being good or evil because of those - of course, for understandable and fairly sympathetic reasons; I’m not saying Sam’s emotional needs aren’t important, but he still (inadvertently, sure, because he’s a good egg but not exactly bright when it comes to other people’s emotions) prioritizes those needs to the point that he makes Jack extremely uncomfortable in 13x03 (and even after Jack expresses his discomfort at being closely watched, Sam tells him he won’t look at him but violates Jack’s boundaries by using the cam), and has to reassess his approach to Jack after Jack protests against his behavior in 13x03 and when Jack confronts him on the things he’d been keeping hidden from him in 13x04.
On the other hand, Dean “It’s the friggin’ devil!” Winchester, treats Jack… like a human being. He quips about him eating fast and questions his age for drinking beer and makes him dig the grave (the grave digging for the salt-and-burn being the hunter thing for excellence in the symbolical language of the show) and purchase food (food being the human thing for excellence in the symbolical language of the show). He treats him with sarcasm. He basically goes ‘cool story bro’ with him. He almost (sure, there’s the whole ‘if you go dark side I’ll take you out’ thing that normally doesn’t happen to regular people) treats Jack like… a younger brother. (An actual younger brother.)
Yes, he “uses” Jack in 13x04 - but in a very blatant, frank manner. Literally getting him to do chores. And Jack does the chores earnestly - he could refuse or protest, like he did with Sam’s attempts to use his powers, but he doesn’t. Sam told him that Dean appreciates effort, and Jack does his best to show Dean he puts effort. It’s a choice. (Notice how two characters accuse another of using them in 13x04 - Jack when confronting Sam, and Mia when confronting Buddy, to which he answers, “Yeah, well, welcome to the world, sweetheart - everybody uses everybody”. Of course the concept of ‘using’ a person is ubiquitous in the show and has recently applied especially to Castiel’s feelings of being a tool, but I don’t want to digress.) I digressed but what I meant to say is that Dean “uses” Jack for physical, very human chores, while Sam has been trying to use Jack for a very supernatural ‘chore’ i.e. saving Mary from the alternate reality.
Basically, if Sam treats Jack like Sam, then Dean treats Jack like Dean (and Dean, as we know, is Humanity). Better posts by other people have discussed how Sam treating someone like Sam implies that Sam seeks goodness is them, while Dean treating someone like Dean implies Dean assuming failure in them; but there’s also the fact that Dean treats Jack in a very human way. Of course, this is not a new thing for them - just think of how, when meeting angels in season 4, Sam treats them like angels (and finds disappointment), Dean immediately start treating them like humans (and finds a very ‘human’ bond with Castiel). There’s some good post out there about how Dean just will treat everything like he would treat a human, almost stubbornly ignoring the inhuman traits of the other person (the other being?) as he’ll evaluate everything with the meter of human morality.
I don’t want to make this post too long, but the point is that Dean will treat everyone like a fellow human being. You know, for the good ol’ sympathy vs empathy thing: Sam will bond with people he identifies with, Dean will treat creatures unlike him like they were human - and they end up identifying with him instead. (And possibly falling in love with him, which is a thing that tends to happen.)
Isn’t that what’s already happening, after all (minus the romantic/sexual part obviously)? Jack has been trying to measure up to Dean, to gain his acceptance and approval and possibly affection. Dean is a beacon of humanity and that’s what Jack is seeking subconsciously - he thinks he wants to be “good” instead of “evil”, but his worldview and his morality are still very naive and narrow, he doesn’t know yet that those words don’t really mean much. What he really wants to be, although he doesn’t realize it yet, is not “good” - it’s “human”. And Sam is speaking that simplistic language of good and evil, which is not fruitful (and will actually do more harm than good to him, because there’s no such thing as being 100% good, and Jack is afraid that not being 100% good means being evil, and that’s upsetting for him…). Dean, on the other hand, is where you need to look when you are seeking humanity. And Jack is already looking at him, imitating him, willing to learn human things from him.
To conclude, I am excited for what’s in store with Jack and the Winchesters, especially if - like I suspect - they actually find Mary/go to the apocalyptic world/people from the apocalyptic world come over here/etc not directly thanks to Jack, and on the other hand Dean’s reasons for being hostile to Jack pass or at least shift in nature and weight (from blame for Cas’ death to jealousy for Cas’ attention, for instance). Some spoilers have suggested that Dean’s and Sam’s attitudes towards Jack will shift somehow, and it’s not surprising because the foundation for a solid Dean-Jack bond are already there, from both sides, even if neither of them fully realizes (or, in Dean’s case, he possibly doesn’t want to get attached to anyone new, regardless of the blame he puts on Jack specifically, because rn, for him, getting attached means pain when you inevitably lose the other people).
Remember how Dean’s big original issue since the beginning of season 1 was that he couldn’t be honest to people? (Yes, the narrative has always been a big closet metaphor, duh) To tell them the truth, and be able to form authentic healthy connections with them (because he knew, from his own words in the pilot, that dishonesty and lies do not allow healthy relationships)? Now look at how he pointedly chooses to be honest to Jack, to tell him the truth, even if that goes against his own self-interest or peace of mind (mind, it’s his truth right now, but still a truth for him). Dean is on a path towards truth, and truth means healthy relationships, authentic connections. And Jack is smacked right on that narrative.