It is true that we can sometimes adapt, but this doesn't account for situations where local events completely transform a destination, making the experience unaffordable or undesirable.
For example, during the Saint-Louis Jazz Festival in Senegal, hotel prices can double or triple, and the city is so crowded that the experience is radically different for a traveler who isn't specifically coming for the festival.
Ignoring this from the start risks ruining an entire trip, which is far from a simple last-minute adjustment.
Major events are an integral part of destination validation, not just a variable to adjust.