The year is decided between November and February. Staffing, purchasing and cash all have to be planned around four months carrying twelve, and treating the summer as a bad patch rather than a structural fact is how these restaurants fail.
Cheese arrives in wheels. Buying in that quantity ties up money and requires storage at the right temperature, and knowing consumption per service is what prevents both running out in December and writing off in April.
Every table has apparatus. Burners, grills, pots and fuel need cleaning between services and replacing on a schedule, and a broken set takes a table out of use on the busiest evening of the year.
December books itself into knots. The same three weeks fill with groups, and without a deposit policy and a firm final-numbers date a restaurant loses tables it could have sold five times over.