From my point of view, it's because the best version is usually the first year, and they start pulling out activities and meals in subsequent years. So I like to do the new itineraries while they still look like what the
ABD developers envisioned. I lucked out that the Scotland trip was still the same in year 2, because they started pulling it apart in year 3. I know it's easier after year 1, but that's been my focus for Iceland & Japan, to experience the "pure" itinerary before people's complaints start diluting the experience.
Sayhello