I have one, but generally only use it nowdays for meter testing and comparisons. In situations where I might use a grey card for shooting I use an incident light meter reading, which more or less amounts to the same thing as a reflective reading off a grey card.

Way back when, I would include one in a test shot on color film so that the printer had a known target for determining the filter pack for the "real" shots.

As for it's use in a hybrid process, that's OT here, but I've never seen the need, especially for b&w.

They can be handy, but aren't essential for most purposes.