Bookings and covers diverge. A book that looks full with tables for two spread across three hours produces a quiet room and a bad night, and only planning by table and by turn time closes that gap.
The no-show is the sector's routine theft. A table for four lost at eight on a Saturday cannot be refilled, and a confirmation the day before recovers most of what a policy alone does not.
Turn times are a real number. Knowing that a table of two takes ninety minutes and a table of six takes two and a half hours is what allows a second sitting without rushing anybody.
Large groups only work with preparation. A deposit and a pre-order for anything over eight protects the kitchen and the evening, and it is normal enough that almost nobody objects.