The thing is, all these things you bought have something to do with the car
. The old car wasn't that big, and to make sure the furniture fitted inside we measured the car, measured the car doors, and bought one that fitted inside perfectly. If we had bought different furniture it wouldn't have fitted inside, and we wouldn't be able to transport it. By measuring exactly we even bought
De Nachtwacht.
Now we are at the point that we are transferring the items to the new car. And even though the new car is bigger, the shape of the car is different, the chairs are bigger and more comfortable, etc. But these same chairs are in the way of putting back the furniture! We have to retrofit all the items we have. With De Nachtwacht we have the choice of either start a completely new painting, or well, take a knife and
cut it 
. With most thing we have chosen to cut it to fit, and then extend it again by making new parts of the painting. We will have De Nachtwacht, and even though some parts are missing, we will make sure it will be better than ever when it is inside the new car!
While driving the old car we also collected many books. These books contains the player data. The new bookcase in our new car sadly also has a slightly different size and the problem is that we can't retrofit the books. We have to buy new books, and copy the pages of the old book on the pages of the new books. Since the page size is different, we have to carefully rewrite these by hand. Some sentences are moved to the next page to make sure it fits, sometimes it is easier to just rewrite the sentence. It's hard and difficult work, but we are trying our best to copy the pages. The point that I want to make here, we can't just photo scan/copy these books in, and print new ones, we really have to do work to make sure everything fits.
While reading the old books we also noticed some oil stains. It seems like the old car was leaking oil somewhere! (imbalanced game, bugs*, etc) Passengers used some books, and while using them, the oil leaked on some of the pages, making some of the pages unreadable. After using the books the passengers carefully put the books back, as instructed, but these stained pages dripped oil, and touched the other books too making them stained too (trading)! In short, these books are tainted. Most books have these oil stains, some only a few pages, some are completely soaked in it. Now we have a choice of buying new books and start over (as intended ~15 years ago), buy new books and write the most important pages in it, or buy new books, write everything in it including all these dirty oil stains! As you may imagine copying oil stains is quite hard. Even when do our best, the stains will still be a little bit different. It is impossible to get exactly the same oil stain. And you could ask yourself, do you want to have a dirty book? Do we want these oil stains? If we keep these, then the new books that we buy later will be stained by it too! To make sure the new car doesn't become dirty 'the best option' is actually by not bringing any books at all. And that includes your favorite book... ('the bes option' as in to keep the car clean, not as in what all the passengers want).
Simply said we try to bring everyone's favorite book, even if it has some oil stains, but we do have to rip out the worst parts. Partly because of the oil stains, and partly cause the new book wouldn't fit the new bookcase otherwise.
-- not really relevant to anything, just me being old: --
*Before when we just bought the car ~15 years ago, no one checked whether their hands were clean or had oil on it(abusing bugs), as we knew it was an old car, and we really didn't care, as we were saving up for the new car anyway. And with only the few books we had, the idea was to buy just new books... During that time there were even passengers (*cough* me */cough* just dipping their books in the oilcan...(Arrow machine gun, casino coins abuse, etc). At some point we had 'too many' passengers aboard and we started checking whether their hands were clean, and whether they were behaving well (GMs). Most of these old oil stains have been cleaned up during these years, but when we an oil stain we never can be certain who made the oilstain or where it came from... We thought it would be a short ride with the old car, but it became 15 years, and we got different insights what to do with the old books.
. They come from original eAthena code 
. What o11c did is: he refactored code. Meanwhile he has been inclined on his own personal efficiency as coder so badly he did it in very high-profile C++. There is joke about C++ every coder speaks own C++; o11c been so inclined he ended up using strange approaches and C++ dialect nobody wants to deal with. I can't judge if it helped o11c's efficiency, but after years passed I think I can draw conclusion it prevented others from understanding code. One have to be more or less become o11c to deal with it reasonably. I guess it isn't easiest feat around though and so far it haven't really worked.