It is just driven by level of bookings and the number of covers they can handle with the available staff.
On Silhouette last year the LCG was under-booked (weather was not ideal) and there were discounts available.
In Murano we were offered a small discount on the lunch as we had several reservations there during the cruise.
Same with Sushi, which was also clearly under-booked most evenings.
Still a lot of people burning through a lot of OBC so combined with ongoing staff shortages, in general, reservations are high so there is a lot less need for the aggressive discount marketing that used to be 'normal'.