Jackson won't leave because if he does, he'll eat humble pie from his folks for ages, But there's also some benefit in the relationship for him, he does seem to have side partners, and Bex having other partners was useful when he was a perpetual student studying something or other.If Becky fucking other dudes and shoving it in Jackson's face didn't make Jackson leave, and if BEING ACCUSED OF FUCKING RAPE didn't make Daniel run far the fuck away and never look back, I don't know what it would actually take for these two chumps to smarten up and ditch the 300 lbs of dead weight that is Becky.
Daniel is a weirder one, he's rude. brash and not as submissive. But has generally been worn down over the years to accept this relationship as a normal for him. Doing better for him might mean dealing with his anger issues and Bex allows him to dodge any of that so maybe that's the charm?