Opening a bottle starts a clock. Whatever is not sold inside its window goes down the sink, and a bar that never counts the glasses obtained from each open bottle loses a percentage point a month without ever seeing it.
The list is a moving document. Wines run out, vintages change and prices move, so a printed list is out of date within a fortnight and an inaccurate one costs the staff an argument at every table.
The cellar is capital sitting still. Bottles bought and kept represent real money, and knowing what is slow, what is appreciating and what should go on the glass list is a financial decision rather than a taste one.
What the staff know decides the average bill. A team that can describe three alternatives sells the second glass, and recording which wines each person struggles with is how training actually happens.