I don't understand the concept.
IMO, a cruise is to get away from the pressure of day to day life. To see the ocean, the sunsets, and starry nights far from the lights of civilization. What's the point in going onto a floating city with throngs of people, massive amounts of lighting, noise, shopping centers, restaurants, gyms, and everything else you left back at home?
If I go on a cruise it's to escape all of that for a while. Give me a three masted schooner that holds around 20 passengers. That's my idea of a vacation.