I don't know... It's just in the flashforwards he's kind of come off the rails. Maybe his working for Ben kind of got the other survivors backs up, or the 'thinking with his heart instead of his head' thing Ben mentioned was something the others couldn't forgive him for. And he has no (known) family, hence no one turning up at the funeral. Perhaps it's just my mind feebly trying to avoid the expected answer that is Michael, or perhaps I actually have a point. It's a mystery
