Hell I met a couple where the wife loved just lounging around on a boat for a week reading and having a few drinks and socializing with her husband and the divers. She'd occasionally snorkel if she felt like it. They did scuba liveaboards together. Wouldn't work if her primary vacation desire was to hit the town.
This could easily be my wife and I. We are up to 19 Liveaboards now with her as a non-diver with another booked for August to celebrate our 30th wedding anniversary. It obviously works for us.