I guess it wouod,be the variety of shows and different resteraunts, shopping both on board and when the cruise stops for onshore visits if they do, plus getting to know others, meeting what could,become lifelong friends and such.
All could be done on land without a cruise, but cruises are becoming more like tsking a vacation. At an exotic spot, (those that stop at different destinations) and offer a lot to do in a relatively “smaller area” than on an actual land vacation spot.
I’ve never been, but onow folks who have and they loved it- I’m too worn out to enjoy a hectic pace like that, but healthier couples who like the party life find lots to do on the ships- there’s just so much entertainment and movies, and dinners to try e5c etc etc- it packs a lot into a short time.
Cruises are for those who lack the will and ability to actually travel.