If you take a compass navigation class, the instructor is likely to teach you how to translate between magnetic bearings and “true” bearings, despite the fact that the grid lines on almost every map printed today are based on true north. One of the key reasons for doing this is to ensure that hikers who have compasses with declination adjustments can communicate with hikers who have compasses without them.
In practice, I find switching between map bearings and magnetic bearings to be unnecessarily taxing on my brain, especially when I need to do it in twilight during a bushwhack in winter. So I own a Suunto M-3 compass with a declination adjustment and do all of my planning and field navigation based on map north, and so do most of the the hikers I hike with.
But I am curious whether other people prefer doing the math or are lazy like me.