Just a guess here but it never did catch on with summer anglers. I know a lot of ice guys really liked them for fishing big baits under tipups but that market is really small.
I replaced nearly every rear treble hook on my cranks with these. In my non-scientific study, I found they made a big difference in hooking percentage. I have quite a few of them left, so maybe I will hold on to them since they will be collectors’ items.