For me, it's a matter of habit and preference.
Early on in my sea kayak journey, with so many "first-time" experiences, I took the approach of minimizing the known from the unknown. Transferring the magnetic north with an arrow often scaled to 1-5 nautical mile(s) provided a welcome reference when paddling with a folded chart in unfamiliar areas, especially in reduced visibility situations of fog or night paddling.
I further forged the habit when creating charts for extended international trips, where I will often cut and copy a chart into manageable pieces.
For me, it's not unlike a spare paddle. 99 times out of 100 I don't need it, but when I do, I'm sure glad I brought it.