People do not like the realization that, no matter how many years Jack spent in the future, he ALWAYS saw himself as a tourist. Even when he used technology. Even when he saved people, which he started to see as more of a burden. He always hated this "aku infested land", and he never gave up on going home, even when all the portals were gone, he kept hoping. Fans tended to just brush his dreams aside, never taking his want to go back to the past seriously. Because they enjoyed the future more, but Jack didn't. Hell, even if Jack didn't have Ashi, he still would have said no to the Scotsman's offer, because why find love when you will eventually leave the future? I'm surprised it never got to anybody just how little Jack cared about the future, never really connecting to it. Jack really only saw the future like a adult would see a child's building block city that he made, as something someone else made, and not part of the real world. Jack doesn't like to see people suffer, but deep down he knows that with all the suffering from Aku over the years, there's tons he couldn't have prevented. He probably walked around imagining Aku just torturing people day in and day out for years, and got used to the idea that the people that live here are used to torture, and his helping won't change anything over all. Sure, they came to help, but Jack still would have seen himself as a failure. When weighting his own family and friends, with centuries worth of people, against the remains of a desolate future, Jack would choose the option with more people every time. Jack always wanted a bland and boring life, and fans didn't.