Wouldn't more time in ports decrease profits since people are not spending money on the ship?
Does the cruiseline receive money from different port areas to bring in the tourists.
You suggest adding ports, After searching out cruises (currently as a hobby since I can't afford one) Doesn't the line offer cruises to multiple ports and others more sea days to cater to the preference of the individual cruiser?
Personally I would enjoy a 7 day cruise at sea. I believe, as one other poster said, the ship is the vacation.