I am guessing that most ARFs nowadays are designed via. CAD and built without plans. Even if the CAD program could print out plans, the manufacturer would have to add annotations/comments, along with some assembly instructions. This would require some effrot, man hours, and money. This fact needs to be balanced against the fact that many people who buy ARFs do not have the skills needed to cut parts from balsa stock and assemble a fuse, wing, etc. from plans. Most ARF owners simply scrap the plane and get a new one. In the end, there is a market for plans, but it seems that the demand might not be enough to justify the effort and expense, from the manufacturer's standpoint.
The only solution I can think of is to buy a second ARF kit, before it's discontinued, if you truly fall in love with the plane. You can then cannibalize the 2nd kit as needed. My father and I did this with my first trainer. I crashed often enough that the parts from the 2nd kit were mostly depleted before I was ready to upgrade to a more advanced plane.