The pool of items are usually all the really old expensive things with a few cheaper but still well loved TC items, so generally whenever you get a holiday bonus item it's worth it. It's also a pretty common chance to get a few each day. This year, we've had the quest givers start in the middle (or more towards the middle) of each holiday, but next year it'll be so much easier to push them right at the start of the holiday. :)

If we split them up via quest givers like books all go to Alexander etc it'd be ... really weird. Fireside has what, 8 books total maybe? It would mean adjusting the odds for each quest based on the pool, so you might not even get a bonus item from Alexander one day because his pool would be so small. It's also important to remember that some of these items, when they did restock, were higher rarity. So the fact they are going out at the same chance rate with the rest of the holiday pool is already working in your favor ;)

We add plenty of items to restocking shops throughout the year already, including some lovely high rarity items like those space backdrops. :) Bringing back these holiday items in the various holiday shops (no holiday shop is never coming back, it's dead forever) doesn't really help get the items out because they are competing with all the other items that restock in the shop. Having them as a bonus chance via quests helps them get out, but we can adjust how often if need be because we can see a lot easier how many are going out.

The month isn't even halfway over yet, don't count out the quest items just yet. ;)