As I've rediscovered time and again while hunting and hiking; if you haven't been to a place in a couple of years you may recognize landmarks but not remember exactly how they fit into your mental map of the area. This kind of problem would have been deadly in places like Greenland, so any kind of mnemonic could be a life saver.

Also, when you are hungry, thirsty and tired, self doubt can be debilitating; a map can give a little extra assurance that you are heading towards fresh water.

They're probably closer to what developers use as "cheat-sheets" - stuff you actually know and have used before, but don't always immediately remember. Maybe some of those coast line routes they only navigated only once a year for some seasonal trades or so.

All the training I had about how to navigate outdoors emphasized that your instincts, particularly in bad weather and/or when you are tired, can be 100% wrong.

Add to that the complexities of trying to navigate from a kayak at sea and I can see why they would develop navigation aids.

It does mention they can be read in the dark, which would definitely be useful if you knew which area you wanted to get to without being able to see it

I'd guess that many generations of accumulated knowledge and experience made them extremely adept at this.

The rest of us are out of practice.