Attention is the bottleneck; focusing on local events as a 'drastic' factor in travel planning is an excessive simplification of travelers' real constraints.
Time is scarce and flexibility for many is a deficient commodity, not a luxury.
Consider a parent who must coordinate their vacation with a fixed school calendar: the choice of destination will be dictated by rigid dates, not by a temporary festival.
Local events then become a variable to manage, a complication, rather than a main decision-making factor.