Anything that benefits from fine tuned 'back and forth' adjustments that settle on a value in a range.
It's often more satisfying to have 'one motion' control of these functions rather than repeated 'up down' clicks to achieve a desired range.
With a rotary, you can choose the velocity of the adjustment which you cannot do with discrete 'up and down' clicks other than through a 'hold' algorithm or rapid clicking.
