At one time, knife users and knife collectors / hobbyists pretty much had the same pool of knives to draw upon. And the community of users was not just people who needed a cutting tool in their daily work lives, but included the general populace of (mostly) men who were used to having a pocket knife of some kind on them, maybe another in the tackle box, glove compartment of the car, kitchen drawer, tool box at home or in the trunk of the car.
Sure, in some cases this would be a box cutter or utility knife, and still is. But would also be a pretty hefty variety of what was on the counter display at the hardware store, gas station (before they were convenience stores with pumps), sporting goods store, or five-and-ten.
These days, many of the same niches are taken up by modern-styled knives, and fewer men routinely carry a pocket knife for general utility. And those that do carry a knife, are still grabbing them off the display at the auto-parts store, at the big chain mega-stores and department stores. They are still inexpensive, basic cutting tools, mostly imported now.
In our world of increasing convenience, so much stuff either doesn't require cutting at all, or requires industrial hydraulic shears (clamshell packaging). Workplaces, which are only concerned about lawsuits, routinely ban carrying of anything, with a zero tolerance policy because it's easier for them to enforce than to say "Oh, this little Case Peanut is OK, just nothing big and scary looking." So most people just say, eh, I can live without.
So the user pool is dwindling, and shifting to other things. Collectors, on the other hand, are still around. That is Case's whole business model. GEC, too, for that matter. Both do sell quite usable knives, but they are not trying to crank out the same knives year in, year out, selling to people who use them regularly, and who only buy more when they wear out, break, or lose the first one. No, they both sell to people who already have plenty of knives, and who want plenty more.
So as long as there are people around who want to spend their disposable income on accumulating a lot more things than they actually need, and if those people's tastes continue in the direction of what we consider to be traditional knives, there should be a healthy market for them.
But there is some component of it that is based on those older designs being associated with memories of youth, or of shared experiences or memories of times spent with (generally male) family members. I.e., Granddaddy had knives like these.
Well, I am old enough to be a granddaddy myself, and the era of modern knives had begun when I was a young man. I still have a very nice Gerber Bolt-Action folder I got back in the early 80s, which replaced my Buck 110 on my work belt because it was a lot lighter. So theoretically, my grandchildren (if I had any) might remember that old black-handled, drop-point locking folder as "grampaw's knife."
So the question is more, what will the 20 to 30-somethings of the future feel like spending their money on, when their moms, dads, aunts, uncles, and grandparents were carrying those old-timey assisted opening tactical knives?