That's a really neat mechanism! If I had to take a stab at why it didn't catch on, I'd say there's a few reasons. The main one is that it's just...different. There's really only two standards in this area that I can tell, the usual punch-down patch panel and the keystone version. The keystone has probably only caught on because it was a popular standard at the drop end, so instead of ordering 100 keystones to terminate your wall plates, you just ordered 200 to terminate the patch panel too. Keystones offer the advantage of being able to move the jacks around a bit if necessary, and identify the line before positioning it in the rack.

Also, while I know you haven't had trouble, I could see that mechanism not working 100% of the time. Maybe a wire doesn't quite get seated properly when the cap is turned or something. I've tried "no tool" keystone jacks before, and they never work quite right. This one looks better but still might have issues.

I went with keystones everywhere and I'm happy with the decision. It's easy to get in a rhythm when terminating those, and the other advantages I mentioned made it kind of a no-brainer. I mostly started this thread to see if there was some obvious thing I was completely missing, but I don't get that sense.