CO is definitely a steady-state tool.
Off-road is so sporadic you only reach steady RPM on smooth single track or when a trail ends and you find yourself on-the-road. 
Indoors on a trainer I use it all the time to spin-up before a HIT interval starts, but also to remind me to throttle RPM down during rest intervals.
The gauge will even inform you when fatigue starts to set in. You’ll find yourself pedaling below your “preferred” cadence during a rest interval, reminding you to spin back up. If it feels easier at a higher RPM it is easier. 
You can also use CO indoors to perform cadence drills (in Slope mode) when a workout supports doing that. Glance at the gauge then deliberately pedal above or below your “normal” pace during the interval.
I also relied on my preferred cadence to determine the gears I needed for my successful run up Mt Washington. I.e. gear range at preferred cadence for target watts required to meet my time goal.
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