As a serious tarot collector, I have a number of rare or extremely rare decks, ranging from 18th and 19th century antiques with "historical significance", through contemporary artists' original works and limited editions, many of which are entirely hand-produced.
I see myself as their current caretaker. I make a reasonable effort to see that they remain well looked after and well preserved, and I try to limit any wear & tear that my handling might add to them, as best I can. I do treat them differently from decks that are commercially produced products, or simply hard(er)-to-find.
As several people have pointed out, a complete rare deck is almost always worth more than the broken up pieces, so there actually aren't a lot of people going around breaking up complete decks and selling individual cards. The few historical cards that are being sold individually on ebay are almost certainly from incomplete decks. Most of the offerings don't sell.
The Rock & Roll has been an odd exception that doesn't actually have very much to do with the overall fate of "rare" or "historically significant" decks out there. In any case, it doesn't have much in common with the hand-painted original 15th c. Cary Yale, or even a late 19th c. Camoin Conver.
I suspect the vast majority of people who go to the trouble and expense of finding and buying decks of significant historical value will do just fine by them. (Rare or unique exceptions aside.)