I have. That said, not all clinicians realize what a wonderful tool it is and how it needn’t be thrown away or glossed over. It can be a wonderful muscle building exercise. It can be a wonderful re-focusing tool for horses that are hot hot hot*. It can be used to balance hot horses before a series of transitions.
To me, it’s worth a LOT more than that measly 10 its capable of earning on a test sheet 
I remember reading (fairly recently? maybe within the last year? maybe it was about Suppenkasper??) a short article on the difficulties of really forward horses and piaffe work and how changing it up with loose rein walk or rein back immediately following isn’t normal, but can be very useful for keeping a hothead chilled out instead of even more amped up during training. As I read it, I was all, phew, maybe I’m not nuts for using RB to settle my nutjob down after piaffe.