People misconstrue cruise liners and cruise ships. Cruise ships are not a direct evolution of cruise liners. Liners were luxury, high speed intercontinental transit for the well heeled. Further, in an increasingly globalized age, liners were the face of a Nation. It was a point of pride to have the most beautiful, fastest, and luxurious cruise liners call into the biggest ports of other nations. The high water mark came with the USS United States in the 50s. With the advent of jets, the rich didn't care if the ride was luxurious, they'd rather spend more time at the destination than a week on board a ship.
The cruise ship was born and, though they initially tried to carry the lines of old liners, the name of the game was increasing passenger numbers. So you get massive, tender boxes full of buffets and norovirus. It's a shame, really.