Why is this difficult to imagine? The capitalists need human labor commodity as long as, well, human labor commodity is the only labor commodity that can do the job. Once it (if ever) isn’t? And they own all the robots that can do the work? And they own all the robot soldiers that can protect their ill-gotten wealth? (Just in short total automation) Well, no need for consumer capitalism any more. Then you just have totalitarian capitalism where everyone else will have to live out their lives at the total mercy of those overlords.

(It doesn’t have to pan out like that. But the point remains that there’s not law of nature that consumer capitalism has to continue, even under Capitalism.)