Some festivities are more major than others. Celebrating the king's coronation day is a good indicator, but if the hero's at court, it's bound to be important to him. Which would be fine if it were therefore important to the plot. There's no guarantee of that. Well, that is, if you don't take after it with tongs and hammer and pound it into shape, fitting two or more necessities of the plot into the events of the festivities, preparing or enjoying (or hating) or cleaning up afterward. Though I have come to the conclusion that you must put in some of the central event, if only to keep the readers from grumbling that after all that preparation, and causing all that clean-up, nothing happened.
There are other events too. If the main character succeeds to a position, from the story point of view, its only purpose may be to give him powers, or inflict duties on him, or both, but there's very likely to be a ceremony of investiture. Which, since it marks the transition, is important in the sense that its occurrence is important. The details aren't, but at least some of them are necessary, even in the baldest summary, to make it convincing.
Such is the life of a writer.