Yes,,,this being ashore is a red herring,,,,,,most people may have one or two alcoholic drinks during the day or none.
Most people who go ashore are back on board for a late lunch unless they are on a 8 hr excursion.
The real drinking is of an evening.
My wife likes a Prosecco,,,at £6.25 she has x2 before dinner,x2 during dinner,x2 after dinner she is quids in with the DP without counting coffee or soft drinks.