I think it exists to power this easter egg?: https://github.com/alphagov/calendars/issues/678 The value I guess depends on whether its appropriate to put up decorations ie a 'celebratory' holiday. It looks like the only non-bunting holidays on there right now are Good Friday (which is more solemn) and Orangemens' Day (which is pretty sectarian), but apparently in the past the Queen's funeral was another non-bunting holiday: https://news.ycombinator.com/item?id=37789437