Does anyone really believe that they’d feel any obligation to resurrect them, even if they could?

Yes, if they have cryonics or its successor technologies for themselves and they can reason about consequences carefully. If you have an injury or pathology in the 24th Century that the health care providers don't know how to treat, you could go into brain preservation to see if the health care providers in, say, the 26th Century would know how to help you. Some of those health care professionals active in the 26th Century might have been born in the 20th or 21st Centuries and have gone through a round or two of brain preservation themselves, and they entered the practice of medicine in the 26th Century as one of their new careers. "Hey, I know this guy. He helped to resuscitate me in 2327. I owe him so I'll return the favor."