Jane links to Lileks, who recently survived an Alaskan cruise, and ponders (as does Lileks) the behavior of most passengers: eat, eat, eat!
One of the reasons often cited for shipboard gluttony, as Jane mentions, is "But it's free!"
Here's the thing: it's not free, it's included in the price you paid when you bought your ticket for the cruise. You've already paid for it.
TANSTAAFL, even if you're on a cruise.