xkcd #3207: Bad Map Projection: Zero Declination
Title text:
'The zero line in WMM2025 passes through a lot of population centers; I wonder what year the largest share of the population lived in a zone of less than 5° of declination,' he thought, derailing all other tasks for the rest of the day.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3207/
Yeah, afaik, there's need for accounting for magnetic North difference from North when navigating even on foot, so it's stated on the map with small enough scale