The answer with more details is: The core of Product Hunt has dead but it could continue to make money because Product Hunt has become a place where people wanting to get traffic has to go but not a website people like to visit.
Just like any social network platform, I think people would do it simply for likes and upvotes and the dopomine that comes with it, but yeah, I'm thinking of adding some sort of points system like karma, reputations, etc.