Along with that, the Ship gets inspected very often, especially after an outbreak of a virus. So, for that reason,too, it's also kept clean and painted and sanitized and scrubbed, etc. On the Caribbean Princess, there was even a soap station on the wall for cruisers to use before handling the utensils, or to wash their hands afterwards -in the Horizon Buffet.
Plus, although it must seem like endless cleaning, the Cruisers enjoy a beautifully clean ship. It's like a 5 star hotel!!