Depends on the trip but it's more like a hotel that shows up in a different city every day, so there's something new all the time if you get off the boat.
My perspective as well. When I was high school and college I went on a few cruises with my elderly grandparents. We had a blast. Every morning you wake up in a new city without the bother of packing bags or spending any time actually going there. Unlike airports, piers are frequently in the oldest most interesting part of the city and you can directly walk to see quite a bit.