One reason why maps were so important for early explorers apart from knowing which direction to travel in and what could be expected to be there was the need for other useful information such as elevation.
What Lies Ahead
By being able to read a map properly you can tell exactly what your exploration party will encounter when it comes to hills or mountains.
By recording the elevation of these forbidding areas, the next person to travel in that region could prepare themselves in ways that the “trailblazers” could not have had the foresight to expect.
Not knowing that at a certain point you will meet a mountain with an elevation that will exceed your abilities meant that many explorers was forced to turn back before they could get to where they really wanted to go.
By having that information ahead of time, the adventure seeker could plan accordingly by packing and carrying the proper supplies to traverse that range safely or even decide to travel a different route to take the mountain out of play.
Both options would be impossible without knowing what you faced before hand.
In addition to being able to tell if there is a mountain or other obstacle in your way with a good map there were other situations that dictated your ability to read a map properly including sovereignty.
Difference Between Life and Death
Not knowing which country, you were in, or in the case of early explorers, which country owned the region you may be traveling in could in some cases mean the difference between life and death depending on the circumstances.
All of these were good reasons for learning the skill of map reading and some cases map writing if the explorer was charting new territory and wanted to preserve a true record for those who may follow them into the previously unknown.