Existing examples, that I've come across at least, are generally a mess and ride more like early proof of concept experiments than something that should ever have been put in the hands of normal people. They're difficult to modulate and add what feels like an arbitrary and unpredictable amount of power to the braking system. This impression of them became more or less entrenched, and that's essentially the last we've seen of them.
But why did it end there so decisively?
In the canti design, instead of completely replacing the pivot with a helical interface, why can't you combine the two? I.e. have a traditional pivot doing most of the work but with a helical interface with a very short, controlled amount of travel layered alongside it to amplify the power up to a certain point. Or, similarly, in a disk brake, couldn't you have traditional pistons but at the end of them there's a little track angled on either side towards the rotor for the pad to get pushed down, similarly adding a controlled amount of braking power?