Yes they are for dealers.
One reason is that I have boxes of them (were free to me). If I purchased they would cost about 5.5 cents each which is the same price as a mount (no hinges for me). I already had some labels but not enough for 500 so I will need labels. I cannot feed them through a printer.
If I had a 1000 3x5 cards (something not common these days), I could print on cards (not sure if big enough to feed) and mount on cards.

I have tested dealer cards in the past for acidity and some have tested positive.
The net is this approach seems practical when not organized for an tradition album and given I want to sort by country not flexible enough for Vario pages. This is more like a topical collection,