Great question!
Along those same lines, something I was wondering about: some knifemakers, even though they have orders on their books, continue to make and sell other knives on a regular basis (e.g., putting other knives up for sale on IG or BF).
I know sometimes it's because the maker is waiting for supplies to come in for the book order, or they sent the blade out for heat treat, but I've also seen it happen other times. I'm curious why - to work on stuff they prefer to work in, in between orders? To keep their listings going as a way of marketing?